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+
+Glans penis
+
+
+External urethral orifice
+
+
+Frenulum of glans
+
+
+506	Fig. 5.74  Superficial features of the perineum in men. A. Overview. B. Close-up of external genitalia.
+Regional Anatomy  •  Perineum	5
+
+
+and  their  associated  musculofascial  coverings,  blood	It defines the external limits of the superficial perineal
+
+vessels, nerves, lymphatics, and drainage ducts descend from the abdomen. The remnant of  the line of  fusion between the labioscrotal swellings in the fetus is visible on the skin of the scrotum as a longitudinal midline raphe that extends from the anus, over the scrotal sac, and onto the inferior aspect of the body of the penis.
+The penis consists of a root and body. The attached root of  the penis is palpable posterior to the scrotum in the urogenital triangle of the perineum.The pendulous part of the penis (body of penis) is entirely covered by skin; the tip of the body is covered by the glans penis.
+The external urethral orifice is a sagittal slit, normally positioned at the tip of the glans. The inferior margin of the urethral orifice is continuous with a midline raphe of the penis, which represents a line of fusion formed in the glans as the urethra develops in the fetus. The base of this raphe  is  continuous  with  the  frenulum  of  the  glans, which is a median fold of skin that attaches the glans to more loosely attached skin proximal to the glans. The base of the glans is expanded to form a raised circular margin (the corona of  the glans); the two lateral ends of  the corona join inferiorly at the midline raphe of the glans. The depression posterior to the corona is the neck of the glans. Normally, a fold of skin at the neck of the glans is continu-ous anteriorly with thin skin that tightly adheres to the glans and posteriorly with thicker skin loosely attached to the body. This fold, known as the prepuce, extends forward to cover the glans. The prepuce is removed during male circumcision, leaving the glans exposed.
+
+Superficial fascia of the urogenital triangle
+The superficial fascia of the urogenital triangle is continu-ous with similar fascia on the anterior abdominal wall.
+As with the superficial fascia of the abdominal wall, the perineal fascia has a membranous layer on its deep surface. This membranous layer (Colles’ fascia), is attached:
+
+■     posteriorly to the perineal membrane and therefore does not extend into the anal triangle (Fig. 5.75), and
+■     to the ischiopubic rami that form the lateral borders of the urogenital triangle and therefore does not extend into the thigh (Fig. 5.75).
+
+pouch, lines the scrotum or labia, and extends around the body of the penis and clitoris.
+Anteriorly, the membranous layer of fascia is continu-ous over the pubic symphysis and pubic bones with the membranous layer of  fascia on the anterior abdominal wall. In the lower lateral abdominal wall, the membranous layer of abdominal fascia is attached to the deep fascia of the thigh just inferior to the inguinal ligament.
+Because the membranous layer of  fascia encloses the superficial perineal pouch and continues up the anterior abdominal wall, fluids or infectious materials that accumu-late in the pouch can track out of the perineum and onto the lower abdominal wall. This material will not track into the anal triangle or the thigh because the fascia fuses with deep tissues at the borders of these regions.
+
+
+
+
+In the clinic
+
+Urethral rupture
+Urethral rupture may occur at a series of well-defined anatomical points.
+The commonest injury is a rupture of the proximal spongy urethra below the perineal membrane. The urethra is usually torn when structures of the perineum are caught between a hard object (e.g., a steel beam or crossbar of a bicycle) and the inferior pubic arch. Urine escapes through the rupture into the superficial perineal pouch and descends into the scrotum and up onto the anterior abdominal wall deep to the superficial fascia.
+In association with severe pelvic fractures, urethral rupture may occur at the prostatomembranous junction above the deep perineal pouch. The urine will extravasate into the true pelvis.
+The worst and most serious urethral rupture is related to serious pelvic injuries where there is complete disruption of the puboprostatic ligaments. The prostate is dislocated superiorly not only by the ligamentous disruption but also by the extensive hematoma formed within the true pelvis. The diagnosis can be made by palpating the elevated prostate during a digital rectal examination.
+
+
+
+
+
+
+
+
+
+
+507
+Pelvis and Perineum
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Membranous layer of superficial fascia
+
+
+Fused to posterior margin of perineal membrane
+
+
+
+A
+
+
+Muscles of abdominal wall
+
+
+
+
+Anterior superior iliac spine
+
+
+
+
+
+Attachment of membranous layer of superficial fascia
+to fascia lata of thigh
+
+
+Inguinal ligament
+
+
+Fascia lata of thigh
+
+
+
+
+
+Posterior margin of	Pubic tubercle B	perineal membrane
+
+Fig. 5.75  Superficial fascia. A. Lateral view. B. Anterior view.
+
+
+
+
+Somatic nerves Pudendal nerve
+The major somatic nerve of the perineum is the pudendal nerve. This nerve originates from the sacral plexus and carries fibers from spinal cord levels S2 to S4. It leaves the pelvic cavity through the greater sciatic foramen inferior to the piriformis muscle, passes around the sacrospinous ligament, and then enters the anal triangle of the perineum
+508	by passing medially through the lesser sciatic foramen. As
+
+
+it enters and courses through the perineum, it travels along the lateral wall of the ischio-anal fossa in the pudendal canal, which is a tubular compartment formed in the fascia  that  covers  the  obturator  internus  muscle. This pudendal canal also contains the internal pudendal artery and accompanying veins.
+The  pudendal  nerve  (Fig.  5.76)  has  three  major terminal branches—the inferior rectal and perineal nerves and the dorsal nerve of the penis or clitoris—which are
+Regional Anatomy  •  Perineum	5
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+S2
+
+S3
+
+
+
+
+Pudendal nerve
+
+
+Obturator internus muscle
+
+
+Pudendal canal in fascia of obturator internus
+
+Inferior rectal nerve
+
+S4
+
+
+
+
+Coccygeus muscle
+
+
+Sacrospinous ligament
+
+
+Levator ani muscle
+Perineal nerve
+
+
+
+Dorsal nerve of penis
+
+Motor branches to skeletal muscle in urogenital triangle
+
+Posterior scrotal nerve
+
+
+
+
+A
+
+Fig. 5.76  Pudendal nerve. A. In men.
+
+
+
+
+509
+Pelvis and Perineum
+
+
+
+Dorsal nerve of clitoris
+
+
+
+
+Motor branches
+
+Posterior labial nerve
+
+
+
+Perineal nerve
+
+Pudendal nerve
+
+
+
+
+
+Inferior rectal nerve
+
+
+
+
+
+
+B
+
+Fig. 5.76, cont’d  B. In women.
+
+
+
+
+accompanied by branches of the internal pudendal artery (Fig. 5.77).
+
+
+Other somatic nerves
+Other somatic nerves that enter the perineum are mainly
+
+
+
+■     The inferior rectal nerve is often multiple, penetrates through the fascia of the pudendal canal, and courses medially across the ischio-anal fossa to innervate the
+
+sensory and include branches of the ilio-inguinal, genito-femoral, posterior femoral cutaneous, and anococcygeal nerves.
+
+external  anal  sphincter  and  related  regions  of  the
+
+levator ani muscles. The nerve is also general sensory for the skin of the anal triangle.
+■     The perineal nerve passes into the urogenital triangle and gives rise to motor and cutaneous branches. The
+
+
+Visceral nerves
+Visceral nerves enter the perineum by two routes:
+
+
+
+motor branches supply skeletal muscles in the superfi-cial  and  deep  perineal  pouches.  The  largest  of  the sensory branches is the posterior scrotal nerve in men and the posterior labial nerve in women.
+■     The dorsal nerve of the penis and clitoris enters the deep perineal pouch (Fig. 5.76). It passes along the lateral margin of the pouch and then exits by passing inferiorly through the perineal membrane in a position just inferior to the pubic symphysis where it meets the body of  the clitoris or the penis. It courses along the dorsal surface of the body to reach the glans. The dorsal nerve is sensory to the penis and clitoris, particularly to
+510	the glans.
+
+■     Those to the skin, which consist mainly of postgangli-onic sympathetics, are delivered into the region along the pudendal nerve. These fibers join the pudendal nerve from gray rami communicantes that connect pelvic parts of the sympathetic trunks to the anterior rami of the sacral spinal nerves (see p. 481 and Fig. 5.62).
+■     Those to erectile tissues enter the region mainly by passing  through  the  deep  perineal  pouch  from  the inferior  hypogastric  plexus  in  the  pelvic  cavity  (see p. 488 and Fig. 5.63B). The fibers that stimulate erec-tion are parasympathetic fibers, which enter the inferior hypogastric plexus via pelvic splanchnic nerves from spinal cord levels of S2 to S4 (see Fig. 5.63A,B).
+Regional Anatomy  •  Perineum	5
+
+
+
+
+Blood vessels Arteries
+The most significant artery of the perineum is the internal pudendal artery (Fig. 5.77). Other arteries entering the area include the external pudendal, the testicular, and the cremasteric arteries.
+
+Internal pudendal artery
+The internal pudendal artery originates as a branch of the anterior trunk of the internal iliac artery in the pelvis (Fig. 5.77). Along with the pudendal nerve, it leaves the pelvis through the greater sciatic foramen inferior to the piriformis muscle. It passes around the ischial spine, where the artery lies lateral to the nerve, enters the perineum by coursing through the lesser sciatic foramen, and accompa-nies the pudendal nerve in the pudendal canal on the
+
+■     A urethral artery also penetrates the perineal mem-brane and supplies the penile urethra and surrounding erectile tissue to the glans.
+■     Near the anterior margin of the deep perineal pouch, the internal pudendal artery bifurcates into two termi-nal branches. A deep artery of the penis penetrates the perineal membrane to enter the crus and supply the crus and corpus cavernosum of the body. The dorsal artery of the penis penetrates the anterior margin of the perineal membrane to meet the dorsal surface of the body of the penis. The vessel courses along the dorsal surface of  the penis, medial to the dorsal nerve, and supplies the glans penis and superficial tissues of  the penis; it also anastomoses with branches of  the deep artery of the penis and the urethral artery.
+
+Branches that supply the erectile tissues in women are
+
+lateral wall of the ischio-anal fossa.	similar to those in men.
+
+The branches of the internal pudendal artery are similar to those of the pudendal nerve in the perineum and include the inferior rectal and perineal arteries, and branches to the erectile tissues of the penis and clitoris (Fig. 5.77).
+
+Inferior rectal arteries
+One or more inferior rectal arteries originate from the internal pudendal artery in the anal triangle and cross the
+
+
+■     Arteries of the bulb of the vestibule supply the bulb of the vestibule and related vagina.
+■     Deep arteries of  the clitoris supply the crura and corpus cavernosum of the body.
+■     Dorsal arteries of  the clitoris supply surrounding tissues and the glans.
+
+
+
+ischio-anal fossa medially to branch and supply muscle and related skin (Fig. 5.77). They anastomose with middle and superior rectal arteries from the internal iliac artery and the inferior mesenteric artery, respectively, to form a network of vessels that supply the rectum and anal canal.
+
+Perineal artery
+The perineal artery originates near the anterior end of the pudendal canal and gives off  a transverse perineal branch, and a posterior scrotal or labial artery to sur-rounding tissues and skin (Fig. 5.77).
+
+Terminal part of the internal pudendal artery
+The terminal part of the internal pudendal artery accom-panies the dorsal nerve of the penis or clitoris into the deep perineal pouch and supplies branches to the tissues in the deep perineal pouch and erectile tissues.
+Branches that supply the erectile tissues in men include the artery to the bulb of the penis, the urethral artery, the deep artery of the penis, and the dorsal artery of the penis (Fig. 5.77).
+
+
+External pudendal arteries
+The external pudendal arteries consist of a superficial vessel and a deep vessel, which originate from the femoral artery in the thigh. They course medially to enter the perineum anteriorly and supply related skin of the penis and scrotum or the clitoris and labia majora.
+
+Testicular and cremasteric arteries
+In  men,  the  testicular  arteries  originate  from  the abdominal aorta and descend into the scrotum through the inguinal canal to supply the testes. Also, cremasteric arteries,  which  originate  from  the  inferior  epigastric branch of the external iliac artery, accompany the sper-matic cord into the scrotum.
+In women, small cremasteric arteries follow the round ligament of the uterus through the inguinal canal.
+
+
+Veins
+Veins in the perineum generally accompany the arteries and join the internal pudendal veins that connect with
+
+
+
+■     The artery of  the bulb of  the penis has a branch that supplies the bulbo-urethral gland and then pene-trates  the  perineal  membrane  to  supply  the  corpus spongiosum.
+
+the internal iliac vein in the pelvis (Fig. 5.78). The excep-tion is the deep dorsal vein of the penis or clitoris that drains mainly the glans and the corpora cavernosa. The
+deep dorsal vein courses along the midline between the	511
+Pelvis and Perineum
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Internal iliac artery
+
+
+
+
+
+Internal pudendal artery
+
+
+
+
+
+
+Inferior rectal artery
+
+Internal pudendal artery in fascia of obturator internus
+
+
+Artery to bulb	Perineal artery
+
+Urethral artery
+
+Deep artery of penis (deep artery of clitoris in women)
+
+
+
+
+Dorsal artery of penis (dorsal artery of clitoris in women)
+
+Artery of bulb of penis
+(artery of vestibular bulb in women)
+
+
+Posterior scrotal artery
+(posterior labial artery in women)
+
+
+
+
+
+Fig. 5.77  Arteries in the perineum.
+
+
+
+
+512
+Regional Anatomy  •  Perineum	5
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Internal pudendal vein
+
+
+
+
+
+Inferior rectal vein
+
+
+
+
+
+
+Prostatic plexus of veins (vesical plexus in women)
+
+Deep dorsal vein (or deep dorsal vein of clitoris in women)
+
+
+Posterior scrotal vein
+(or posterior labial vein in women)
+
+
+
+
+
+
+
+Fig. 5.78  Perineal veins.
+
+
+
+
+513
+Pelvis and Perineum
+
+
+dorsal arteries on each side of  the body of  the penis or	Lymphatic  channels  from  superficial  tissues  of  the
+
+clitoris, passes though the gap between the inferior pubic ligament and the deep perineal pouch, and connects with the plexus of  veins surrounding the prostate in men or bladder in women.
+External pudendal veins, which drain anterior parts of the labia majora or the scrotum and overlap with the area of drainage of the internal pudendal veins, connect with the femoral vein in the thigh. Superficial dorsal veins of the penis or clitoris that drain skin are tributaries of the exter-nal pudendal veins.
+
+Lymphatics
+Lymphatic vessels from deep parts of the perineum accom-pany the internal pudendal blood vessels and drain mainly into internal iliac nodes in the pelvis.
+
+penis or the clitoris accompany the superficial external pudendal blood vessels and drain mainly into superficial inguinal  nodes,  as  do  lymphatic  channels  from  the scrotum or labia majora (Fig. 5.79). The glans penis, glans clitoris, labia minora, and terminal inferior end of  the vagina drain into deep inguinal nodes and external iliac nodes.
+Lymphatics  from  the  testes  drain  via  channels  that ascend in the spermatic cord, pass through the inguinal canal,  and  course  up  the  posterior  abdominal  wall  to connect directly with lateral aortic or lumbar nodes and pre-aortic nodes around the aorta, at approximately vertebral  levels  LI  and  LII. Therefore  disease  from  the testes  tracks  superiorly  to  nodes  high  in  the  posterior abdominal wall and not to inguinal or iliac nodes.
+
+
+
+
+
+
+Thoracic duct
+
+
+Pre-aortic nodes	LI
+
+Lateral aortic (lumbar) nodes
+Lymph from testis
+
+
+External iliac nodes
+
+
+
+Inguinal ligament
+
+
+
+Deep inguinal nodes
+
+Superficial inguinal nodes
+
+
+
+
+Testis
+
+
+
+
+
+Lymph from glans penis (glans clitoris, labia minora, and lower part of vagina
+in women)
+
+Lymph from superficial tissues of penis and scrotum
+(clitoris and labia majora in women)
+
+
+514	Fig. 5.79  Lymphatic drainage of the perineum.
+Surface Anatomy  •  How to Define the Margins of the Perineum	5
+
+
+Surface anatomy
+Surface anatomy of the pelvis and perineum	symphysis lie in the same vertical plane. The pelvic inlet Palpable   bony   features   of   the   pelvis   are   used   as	faces  anterosuperiorly.  The  urogenital  triangle  of   the landmarks for:	perineum is oriented in an almost horizontal plane and
+
+
+■     locating soft tissue structures,
+■     visualizing the orientation of the pelvic inlet, and ■     defining the margins of the perineum.
+
+The  ability  to  recognize  the  normal  appearance  of
+
+faces inferiorly, whereas the anal triangle is more vertical and faces posteriorly (Figs. 5.80 and 5.81).
+
+How to define the margins of the perineum
+The pubic symphysis, ischial tuberosities, and tip of  the sacrum are palpable on patients and can be used to define
+
+
+
+structures in the perineum is an essential part of a physical examination.
+In  women,  the  cervix  can  be  visualized  directly  by opening the vaginal canal using a speculum.
+
+the boundaries of  the perineum. This is best done with patients lying on their backs with their thighs flexed and abducted in the lithotomy position (Fig. 5.82).
+
+
+
+In men, the size and texture of the prostate in the pelvic cavity can be assessed by digital palpation through the anal aperture.
+
+
+Orientation of the pelvis and perineum in the anatomical position
+
+In  the  anatomical  position,  the  anterior  superior  iliac
+
+■     The ischial tuberosities are palpable on each side as large bony masses near the crease of skin (gluteal fold) between the thigh and gluteal region. They mark the lateral corners of the diamond-shaped perineum.
+■     The tip of the coccyx is palpable in the midline posterior to the anal aperture and marks the most posterior limit of the perineum.
+■     The anterior limit of the perineum is the pubic symphy-
+
+spines  and  the  anterior  superior  edge  of   the  pubic	sis. In women, this is palpable in the midline deep to the
+
+
+
+
+
+
+
+
+
+
+
+High point of iliac crest
+
+Tuberculum of iliac crest
+
+Anterior superior iliac spine
+
+
+Posterior superior iliac spine
+
+
+
+Plane of pelvic inlet
+
+
+
+
+
+
+
+
+Pubic tubercle
+A
+
+Plane of urogenital triangle	Plane of anal triangle
+B
+
+
+Fig. 5.80  Lateral view of the pelvic area with the position of the skeletal features indicated. The orientation of the pelvic inlet, urogenital
+triangle, and anal triangle is also shown. A. In a woman. B. In a man.	515
+Pelvis and Perineum
+
+
+
+
+
+
+
+Position of pubic symphysis
+
+Anterior superior iliac spine
+
+
+Pubic tubercle
+
+
+
+
+A	B
+
+Fig. 5.81  Anterior view of the pelvic area. A. In a woman showing the position of the pubic symphysis. B. In a man showing the position of the pubic tubercle, pubic symphysis, and anterior superior iliac spine.
+
+
+
+
+
+Pubic symphysis
+
+
+
+
+Approximate position of perineal body (central tendon)
+Ischial tuberosity
+
+Urogenital triangle
+
+
+Ischial tuberosity
+
+
+Anal triangle
+
+
+Coccyx
+A
+
+
+
+
+
+
+Mons pubis	Pubic symphysis
+
+
+
+Urogenital triangle
+Approximate position of perineal body (central tendon)
+
+
+Ischial tuberosity
+
+Gluteal fold
+
+Gluteal region
+
+
+B
+
+Ischial tuberosity
+
+Anal triangle
+
+Coccyx
+
+
+Fig. 5.82  Inferior view of the perineum in the lithotomy position. Boundaries, subdivisions, and palpable landmarks are indicated. A. In a man. 516	B. In a woman.
+Surface Anatomy  •  Identification of Structures in the Anal Triangle	5
+
+
+
+mons pubis. In men, the pubic symphysis is palpable immediately superior to where the body of  the penis joins the lower abdominal wall.
+
+Imaginary lines that join the ischial tuberosities with the pubic symphysis in front, and with the tip of the coccyx behind, outline the diamond-shaped perineum. An addi-tional  line  between  the  ischial  tuberosities  divides  the perineum into two triangles, the urogenital triangle ante-riorly and anal triangle posteriorly. This line also approxi-mates the position of the posterior margin of the perineal membrane. The midpoint of this line marks the location of the perineal body or central tendon of the perineum.
+
+
+Identification of structures in the anal triangle
+
+The anal triangle is the posterior half of the perineum. The base of the triangle faces anteriorly and is an imaginary line joining the two ischial tuberosities. The apex of the triangle is the tip of the coccyx; the lateral margins can be approximated by lines joining the coccyx to the ischial tuberosities. In both women and men, the major feature of the anal triangle is the anal aperture in the center of the triangle. Fat fills the ischio-anal fossa on each side of the anal aperture (Fig. 5.83).
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Position of perineal body
+
+
+Ischial tuberosity Position of ischio-anal fossa
+Anal triangle
+
+Coccyx
+
+
+Ischial tuberosity
+Position of ischio-anal fossa
+
+Anal aperture
+
+
+
+A
+
+
+
+
+
+
+Labium minus
+
+
+Position of perineal body
+
+
+
+Position of ischio-anal fossa Anal triangle
+Coccyx
+
+Ischial tuberosity
+Position of ischio-anal fossa
+
+Anal aperture
+
+
+
+B
+
+Fig. 5.83  Anal triangle with the anal aperture and position of the ischio-anal fossae indicated. A. In a man. B. In a woman.	517
+Pelvis and Perineum
+
+
+
+
+Identification of structures in the urogenital triangle of women
+
+The urogenital triangle is the anterior half of the perineum. The base of the triangle faces posteriorly and is an imagi-nary line joining the two ischial tuberosities. The apex of the triangle is the pubic symphysis. The lateral margins can be approximated by lines joining the pubic symphysis to the ischial tuberosities. These lines overlie the ischiopubic rami, which can be felt on deep palpation.
+In women, the major contents of the urogenital triangle are the clitoris, the vestibule, and skin folds that together form the vulva (Fig. 5.84A,B).
+
+Two thin skin folds, the labia minora, enclose between them a space termed the vestibule into which the vagina and the urethra open (Fig. 5.84C). Gentle lateral traction on the labia minora opens the vestibule and reveals a soft tissue mound on which the urethra opens. The para-urethral (Skene’s) glands, one on each side, open into the skin crease between the urethra and the labia minora (Fig. 5.84D).
+Posterior to the urethra is the vaginal opening. The vaginal opening (introitus) is ringed by remnants of the hymen that originally closes the vaginal orifice and is usually ruptured during the first sexual intercourse. The ducts of the greater vestibular (Bartholin’s) glands, one on
+
+
+
+
+
+
+Skin overlying body of clitoris
+
+Glans clitoris
+
+Prepuce (hood) of clitoris	Glans clitoris
+
+
+
+Frenulum of clitoris
+
+
+Labium Labium minus	minus
+
+Vestibule Labium majus
+
+
+
+
+
+Posterior commissure (overlies perineal body)
+
+B
+
+Vaginal opening	External urethral orifice A	(introitus)
+
+
+
+
+Glans clitoris
+
+
+
+
+External urethral orifice
+
+Vaginal opening
+
+Remnants of hymen
+
+Area of opening of the duct of the para-urethral gland
+
+Area of opening of the duct of the greater vestibular gland
+
+
+Fourchette
+
+C	D
+
+Fig. 5.84  Structures in the urogenital triangle of a woman. A. Inferior view of the urogenital triangle of a woman with major features indicated. B. Inferior view of the vestibule. The labia minora have been pulled apart to open the vestibule. Also indicated are the glans clitoris, the clitoral hood, and the frenulum of the clitoris. C. Inferior view of the vestibule showing the urethral and vaginal orifices and the hymen. The labia minora have been pulled further apart than in Figure 5.84B. D. Inferior view of the vestibule with the left labium minus pulled to the side to
+518	show the regions of the vestibule into which the greater vestibular and para-urethral glands open.
+Surface Anatomy  •  Identification of Structures in the Urogenital Triangle of Men	5
+
+
+Skin overlying body of clitoris
+Mons pubis
+Body of clitoris (unattached
+parts of corpora cavernosa)	Glans clitoris
+
+
+
+
+
+
+
+Anterior fornix
+
+
+
+Posterior fornix
+
+
+Cervix
+
+External cervical os
+
+
+
+F
+
+
+
+
+E
+
+Crus clitoris (attached part of corpus cavernosum)
+
+Bulb of vestibule
+
+Greater vestibular gland
+
+
+Fig. 5.84, cont’d  E. View through the vaginal canal of the cervix. F. Inferior view of the urogenital triangle of a woman with the erectile tissues of the clitoris and vestibule and the greater vestibular glands indicated with overlays.
+
+
+
+
+
+each side, open into the skin crease between the hymen and the adjacent labium minus (Fig. 5.84D).
+The labia minora each bifurcate anteriorly into medial and lateral folds. The medial folds unite at the midline to form the frenulum of the clitoris. The larger lateral folds also unite across the midline to form the clitoral hood or prepuce that covers the glans clitoris and distal parts of the body of  the clitoris. Posterior to the vaginal orifice, the labia minora join, forming a transverse skin fold (the fourchette).
+The labia majora are broad folds positioned lateral to the labia minora. They come together in front to form the mons pubis, which overlies the inferior aspect of the pubic sym-physis. The posterior ends of the labia majora are separated by a depression termed the posterior commissure, which overlies the position of the perineal body.
+The cervix is visible when the vaginal canal is opened with a speculum (Fig. 5.84E). The external cervical os opens onto the surface of the dome-shaped cervix. A recess or gutter, termed the fornix, occurs between the cervix and the vaginal wall and is further subdivided, based on loca-tion, into anterior, posterior, and lateral fornices.
+The roots of the clitoris occur deep to surface features of the perineum and are attached to the ischiopubic rami and the perineal membrane.
+
+The bulbs of  the vestibule (Fig. 5.84F), composed of erectile tissues, lie deep to the labia minora on either side of the vestibule. These erectile masses are continuous, via thin bands of erectile tissues, with the glans clitoris, which is visible under the clitoral hood. The greater vestibular glands occur posterior to the bulbs of  the vestibule on either side of the vaginal orifice.
+The crura of the clitoris are attached, one on each side, to the ischiopubic rami. Each crus is formed by the attached part of the corpus cavernosum. Anteriorly, these erectile corpora detach from bone, curve posteroinferiorly, and unite to form the body of the clitoris.
+The body of  the clitoris underlies the ridge of  skin immediately anterior to the clitoral hood (prepuce). The glans clitoris is positioned at the end of the body of the clitoris.
+
+Identification of structures in the urogenital triangle of men
+
+In men, the urogenital triangle contains the root of  the penis. The testes and associated structures, although they migrate into the scrotum from the abdomen, are generally evaluated with the penis during a physical examination.
+The scrotum in men is homologous to the labia majora
+in women. Each oval testis is readily palpable through the	519
+Pelvis and Perineum
+
+
+
+skin of the scrotum (Fig. 5.85A). Posterolateral to the testis is an elongated mass of tissue, often visible as a raised ridge that contains lymphatics and blood vessels of  the testis, and the epididymis and ductus deferens. A midline raphe (Fig. 5.85B) is visible on the skin separating left and right sides of  the scrotum. In some individuals, this raphe is prominent and extends from the anal aperture, over the scrotum and along the ventral surface of the body of the penis, to the frenulum of the glans.
+The root of the penis is formed by the attached parts of the corpus spongiosum and the corpora cavernosa. The corpus spongiosum is attached to the perineal membrane and can be easily palpated as a large mass anterior to the
+
+perineal body. This mass, which is covered by the bulbo-spongiosus muscles, is the bulb of penis.
+The  corpus  spongiosum  detaches  from  the  perineal membrane anteriorly, becomes the ventral part of the body of the penis (shaft of penis), and eventually terminates as the expanded glans penis (Fig. 5.85C,D).
+The crura of the penis, one crus on each side, are the attached parts of the corpora cavernosa and are anchored to the ischiopubic rami (Fig. 5.85E). The corpora cavernosa are unattached anteriorly and become the paired erectile masses that form the dorsal part of the body of the penis. The glans penis caps the anterior ends of  the corpora cavernosa.
+
+
+
+
+
+
+Body of penis
+Glans penis
+
+Testis
+
+Epididymis, vas deferens, vessels, nerves, and lymphatics
+
+
+
+
+Position of perineal body		Ischial tuberosity A
+
+
+
+
+
+Glans penis
+
+Frenulum
+
+Ventral surface of body of penis
+
+
+
+Raphe
+
+
+
+
+Testis
+
+
+
+B
+
+520	Fig. 5.85  Structures in the urogenital triangle of a man. A. Inferior view. B. Ventral surface of the body of the penis.
+Surface Anatomy  •  Identification of Structures in the Urogenital Triangle of Men	5
+
+
+
+
+Dorsal surface of body of penis
+
+
+
+
+Urethral orifice
+
+
+
+Neck of glans
+
+Corona of glans Prepuce
+Glans penis
+
+
+
+C
+
+
+
+
+Body of penis (unattached parts of corpus spongiosum and corpora cavernosa)
+
+D
+
+
+
+
+
+Glans penis
+
+
+
+Crus of penis (attached part of corpus cavernosum)
+
+Bulb of penis (attached part of corpus spongiosum)
+
+Position of perineal body
+E
+
+Fig. 5.85, cont’d  C. Anterior view of the glans penis showing the urethral opening. D. Lateral view of the body of the penis and glans. E. Inferior view of the urogenital triangle of a man with the erectile tissues of the penis indicated with overlays.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+521
+Pelvis and Perineum
+
+
+Clinical cases
+
+
+Case 1 VARICOCELE
+A 25-year-old man visited his family physician because he had a “dragging feeling” in the left side of his scrotum. He was otherwise healthy and had no other symptoms. During examination, the physician palpated the left testis, which was normal, although he noted soft nodular swelling around the superior aspect of the testes and the epididymis. In his clinical notes, he described these findings as a “bag of worms” (Fig. 5.86). The bag of worms was a varicocele.
+
+The venous drainage of the testis is via the pampiniform plexus of veins that runs within the spermatic cord. A varicocele is a collection of dilated veins that arise from the pampiniform plexus. In many ways, they are similar to varicose veins that develop in the legs. Typically, the patient complains of a dragging feeling in the scrotum and around the testis, which is usually worse toward the end of the day.
+
+The family physician recommended surgical treatment, with a recommendation for surgery through an inguinal incision.
+
+A simple surgical technique divides the skin around the inguinal ligament. The aponeurosis of the external
+oblique muscle is divided in the anterior abdominal wall to display the spermatic cord. Careful inspection of the spermatic cord reveals the veins, which are surgically ligated.
+
+Another option is to embolize the varicocele.
+
+In this technique, a small catheter is placed via the right femoral vein. The catheter is advanced along the external iliac vein and the common iliac vein and into the inferior vena cava. The catheter is then positioned in the left renal vein, and a venogram is performed to demonstrate the origin of the left testicular vein. The catheter is advanced down the left testicular vein into the veins of the inguinal canal and the pampiniform plexus. Metal coils to occlude the vessels are injected, and the catheter is withdrawn.
+
+The patient asked how blood would drain from the testis after the operation.
+
+
+
+Left testicular vein
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Penis	Pampiniform plexus
+
+
+
+Although the major veins of the testis had been occluded, small collateral veins running within the scrotum and around the outer aspect of the spermatic cord permitted drainage without recurrence of the varicocele.
+
+
+Fig. 5.86  Left testicular venogram demonstrating the pampiniform plexus of veins.
+
+
+
+
+
+
+
+
+522
+Clinical Cases  •  Case 2	5
+
+
+Case 2
+
+PELVIC KIDNEY	Pelvic kidney	Sacrum
+
+
+A young woman visited her family practitioner because she had mild upper abdominal pain. An ultrasound demonstrated gallstones within the gallbladder, which explained the patient’s pain. However, when the technician assessed the pelvis, she noted a mass behind the bladder, which had sonographic findings similar to a kidney
+(Fig. 5.87).
+
+What did the sonographer do next? Having demonstrated this pelvic mass behind the bladder, the sonographer assessed both kidneys. The patient had a normal right kidney. However, the left kidney could not be found in its usual place. The technician diagnosed a pelvic kidney.
+
+A pelvic kidney can be explained by the embryology. The kidneys develop from a complex series of structures that originate adjacent to the bladder within the fetal pelvis. As development proceeds and the functions of the various parts of the developing kidneys change, they attain a superior position in the upper abdomen adjacent to the abdominal aorta and inferior vena cava, on the posterior abdominal wall. A developmental arrest or complication may prevent the kidney from obtaining its usual position. Fortunately, it is unusual for patients to have any symptoms relating to a pelvic kidney.
+
+This patient had no symptoms attributable to the pelvic kidney and she was discharged.
+
+
+L3
+
+
+L4
+
+
+
+L5
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Bladder	Rectum
+
+Fig. 5.87  Sagittal computed tomogram demonstrating a pelvic kidney.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+523
+Pelvis and Perineum
+
+
+
+Case 3 OVARIAN TORSION
+A 19-year-old woman presented to the emergency department with a 36-hour history of lower abdominal pain that was sharp and initially intermittent, later becoming constant and severe. The patient also reported feeling nauseated and vomited once in the ER. She did not have diarrhea and had opened her bowels normally 8 hours before admission. She had no symptoms of dysuria. She was afebrile, slightly tachycardic at 95/min, and had a normal blood pressure. Blood results showed mild leukocytosis of 11.6 x 109/L and normal renal and liver function tests. She reported being sexually active with a long-term partner. She was never pregnant, and the urine pregnancy test on admission was negative.
+
+On physical examination there was tenderness in the right iliac fossa with guarding. On vaginal examination a tender mass in the right adnexal region was felt. The patient subsequently underwent a transvaginal ultrasound examination for evaluation of adnexal pathology. The scan showed a markedly enlarged right ovary measuring up to 8 cm in long axis with echogenic stroma and peripherally distributed follicles. There was no internal vascularity when
+color Doppler was applied. A small amount of free fluid was seen in the pouch of Douglas. The diagnosis of ovarian torsion was made.
+
+Ovarian torsion is the twisting of an ovary on its suspensory ligament, which contains arterial, venous, and lymphatic
+
+
+
+vessels (forming so-called vascular pedicle), leading to a compromised blood supply. Initially, the venous and lymphatic circulation is compromised, resulting in ovarian edema and enlargement. The arterial flow is maintained longer due to thicker and less compressible arterial walls. Prolonged torsion leads to increased internal ovarian pressure that eventually results in arterial thrombosis, ischemia of the ovarian tissue, and necrosis. If the correct diagnosis and treatment are delayed, the patient may develop generalized sepsis.
+
+The symptoms are nonspecific, making the diagnosis of ovarian torsion challenging. There is often no significant past medical history.
+
+At surgery, the right ovary was hemorrhagic and necrotic with the pedicle twisted 360 degrees. The left ovary was normal in appearance. Right-sided salpingo-oophorectomy was performed, and histopathological examination confirmed completely necrotic ovary without any residual normal ovarian tissue. The patient made a quick recovery after surgical intervention.
+
+Ovarian torsion is encountered in women of all ages, but those of reproductive age have much higher prevalence. Torsion of a normal ovary is uncommon and is seen more frequently in adolescent population, with elongated pelvic ligaments, fallopian tube spasm, or more mobile fallopian tubes or mesosalpinx cited as contributing factors.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+524
+Clinical cases  •  Case 5	5
+
+
+
+Case 4
+
+SCIATIC NERVE COMPRESSION
+
+A young man developed pain in his right gluteal region, in the posterior aspect of the thigh and around the posterior and lateral aspects of the leg. On further questioning, he reported that the pain also radiated over the lateral part of the foot, particularly around the lateral malleolus.
+
+The areas of pain correspond to dermatomes L4 to S3 nerves.
+
+Over the following weeks, the patient began to develop muscular weakness, predominantly footdrop.
+
+These findings are consistent with loss of the motor function and sensory change in the common fibular
+
+
+
+
+
+
+Case 5
+
+LEFT COMMON ILIAC ARTERY OBSTRUCTION
+
+A 65-year-old man was examined by a surgical intern because he had a history of buttock pain and impotence. On examination he had a reduced peripheral pulse on
+the left foot compared to the right. On direct questioning, the patient revealed that he experienced severe left-sided buttock pain after walking 100 yards. After a short
+period of rest, he could walk another 100 yards before the same symptoms recurred. He also noticed that
+over the past year he was unable to obtain an erection. He smoked heavily and was on no other drugs or treatment.
+
+The pain in the left buttock is ischemic in nature. He gives a typical history relating to lack of blood flow to the muscles. A similar finding is present when muscular branches of the femoral artery are occluded or stenosed. Such patients develop similar (ischemic) pain in the calf muscles called intermittent claudication.
+
+
+
+nerve, which is a branch of the sciatic nerve in the lower limb.
+
+A computed tomography (CT) scan of the abdomen and pelvis revealed a mass in the posterior aspect of the right side of the pelvis. The mass was anterior to the piriformis muscle and adjacent to the rectum.
+
+On the anterior belly of the piriformis muscle, the sciatic nerve is formed from the roots of L4 to S3 nerves. The mass in the patient’s pelvis compressed this nerve, producing his sensory and motor dysfunction.
+
+During surgery, the mass was found to be a benign nerve tumor and was excised. This patient had no long-standing neurological deficit.
+
+
+
+
+
+
+
+
+How does the blood get to the gluteal muscles?
+
+Blood arrives at the aortic bifurcation and then passes
+into the common iliac arteries, which divide into the internal and external iliac vessels. The internal iliac artery then divides into anterior and posterior divisions, which in
+turn give rise to vessels that leave the pelvis by passing through the greater sciatic foramen and supply the gluteal muscles. The internal pudendal artery also arises from the anterior division of the internal iliac artery and supplies the penis.
+
+The patient’s symptoms occur on the left side, suggesting that an obstruction exists on that side only.
+
+Because the patient’s symptoms occur on the left side only, the lesion is likely in the left common iliac artery (eFig. 5.88) and is preventing blood flow into the external and internal iliac arteries on the left side.
+(continues)
+
+
+
+
+
+
+
+
+
+
+
+
+
+524.e1
+Pelvis and Perineum
+
+
+
+Case 5—cont’d
+
+“How will I be treated?” asked the patient.
+
+The patient was asked to stop smoking and begin regular exercise. Other treatment options include unblocking the lesion by ballooning the blockage to reopen the vessels or by a surgical bypass graft.
+
+
+
+Stopping smoking and regular exercise improved the patient’s walking distance. The patient underwent the less invasive procedure of ballooning the vessel (angioplasty) and as a result he was able to walk unhindered and to have an erection.
+
+
+Left common iliac artery
+Aorta	Lumbar artery
+Occluded left common iliac artery
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+A
+
+
+Left internal iliac artery
+Right internal iliac artery	Left external iliac artery
+Right external iliac artery
+
+
+B
+
+Patent right iliac system
+
+
+eFig. 5.88  Digital subtraction aorto-iliac angiogram. A. Normal circulation pattern. B. Occluded left common iliac artery.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+524.e2
+Clinical cases  •  Case 7	5
+
+
+
+Case 6
+
+IATROGENIC URETERIC INJURY
+
+A 50-year-old woman was admitted to hospital for surgical resection of the uterus (hysterectomy) for cancer. The surgeon was also going to remove all the pelvic lymph nodes and carry out a bilateral salpingo-oophorectomy (removal of uterine tubes and ovaries). The patient was prepared for this procedure and underwent routine surgery. Twenty-five hours after surgery, it was noted that the patient had passed no urine and her abdomen was expanding. An ultrasound scan demonstrated a considerable amount of fluid within the abdomen. Fluid withdrawn from the abdomen was tested and found to be urine.
+
+It was postulated that this patient’s ureters had been damaged during the surgery.
+
+The pelvic part of the ureter courses posteroinferiorly and external to the parietal peritoneum on the lateral wall of the
+
+
+
+
+
+
+Case 7
+
+ECTOPIC PREGNANCY
+
+A 25-year-old woman was admitted to the emergency department with a complaint of pain in her right iliac fossa. The pain had developed rapidly over approximately 40 minutes and was associated with cramps and vomiting. The surgical intern made an initial diagnosis of appendicitis.
+
+The typical history for appendicitis is a central abdominal, colicky (intermittent waxing and waning) pain, which over a period of hours localizes to become a constant pain in the right iliac fossa. The central colicky pain is typical for a poorly localized visceral type of pain. As the parietal peritoneum becomes inflamed, the pain becomes localized. Although this patient does have right iliac fossa pain, the history is not typical for appendicitis (although it must be remembered that patients may not always have a classical history for appendicitis).
+
+The surgical intern asked a more senior colleague for an opinion.
+
+The senior colleague considered other anatomical structures that lie within the right iliac fossa as a potential cause of pain. These include the appendix, the cecum, and the small
+
+
+
+pelvis anterior to the internal iliac artery. It continues in its course to a point approximately 2 cm superior to the ischial spine and then passes anteromedially and superior to the levator ani muscles. Importantly, the ureter closely adheres to the peritoneum. The only structure that passes between the ureter and the peritoneum in men is the ductus deferens. In women, however, as the ureter descends on the pelvic wall, it passes under the uterine artery. The ureter continues close to the lateral fornix of the vagina, especially on the left, and enters the posterosuperior angle of the bladder.
+It was at this point that the ureter was inadvertently damaged.
+
+Knowing the anatomy and recognizing the possibility of ureteric damage enabled the surgeons to reestablish continuity of the ureter surgically. The patient was hospitalized a few days longer than expected and made an uneventful recovery.
+
+
+
+
+
+
+
+
+bowel. Musculoskeletal pain and referred pain could also be potential causes. In women, pain may also arise from the ovary, fallopian tube, and uterus. In a young patient, diseases of these organs are rare. Infection and pelvic inflammatory disease may occur in the younger patient and need to be considered.
+
+The patient gave no history of these disorders.
+
+Upon further questioning, however, the patient revealed that her last menstrual period was 6 weeks before this examination. The senior physician realized that a potential cause of the abdominal pain was a pregnancy outside the uterus (ectopic pregnancy). The patient was rushed for an abdominal ultrasound, which revealed no fetus or sac in the uterus. She was also noted to have a positive pregnancy test. The patient underwent surgery and was found to have
+a ruptured fallopian tube caused by an ectopic pregnancy.
+
+Whenever a patient has apparent pelvic pain, it is important to consider the gender-related anatomical differences. Ectopic pregnancy should always be considered in women of childbearing age.
+
+
+
+
+
+524.e3
+Pelvis and Perineum
+
+
+
+Case 8 UTERINE TUMOR
+A 35-year-old woman visited her family practitioner because she had a “bloating” feeling and an increase in abdominal girth. The family practitioner examined the lower abdomen, which revealed a mass that extended from the superior pubic rami to the level of the umbilicus. The superior margin of the mass was easily palpated, but the inferior margin appeared to be less well defined.
+
+This patient has a pelvic mass.
+
+When examining a patient in the supine position, the observer should uncover the whole of the abdomen.
+
+Inspection revealed a bulge in the lower abdomen to the level of the umbilicus. Palpation revealed a hard and slightly irregular mass with well-defined superior and lateral borders and a less well-defined inferior border, giving the impression that the mass continued into the pelvis. The lesion was dull to percussion. Auscultation did not reveal any abnormal sounds.
+
+The doctor pondered which structures this mass may be arising from. When examining the pelvis, it is important to remember the sex differences. Common to both men and women are the rectum, bowel, bladder, and musculature. Certain pathological states are also common to both sexes, including the development of pelvic abscesses and fluid collections.
+
+In men, the prostate cannot be palpated transabdominally, and it is extremely rare for it to enlarge to such an extent in benign diseases. Aggressive prostate cancer can spread
+
+
+
+throughout the whole of the pelvis, although this is often associated with bowel obstruction and severe bladder symptoms.
+
+In women, a number of organs can develop large masses, including the ovaries (solid and cystic tumors), the embryological remnants within the broad ligaments, and the uterus (pregnancy and fibroids).
+
+The physician asked further questions.
+
+It is always important to establish whether the patient is pregnant (occasionally, pregnancy may come as a surprise to the patient).
+
+This patient’s pregnancy test was negative. After the patient emptied her bladder, there was no change in the mass. The physician thought the mass might be a common benign tumor of the uterus (fibroid). To establish the diagnosis, he obtained an ultrasound scan of the pelvis, which confirmed that the mass stemmed from the uterus.
+
+The patient was referred to a gynecologist, and after a long discussion regarding her symptomatology, fertility, and risks, the surgeon and the patient agreed that a hysterectomy (surgical removal of the uterus) would be an appropriate course of therapy.
+
+The patient sought a series of opinions from other gynecologists, all of whom agreed that surgery was the appropriate option.
+
+The fibroid was removed with no complications.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+524.e4
+Clinical cases  •  Case 9	5
+
+
+
+Case 9 UTERINE FIBROIDS
+A 52-year-old woman was referred to a gynecologist. Magnetic resonance imaging (MRI) indicated the presence of uterine fibroids. After a long discussion regarding her symptomatology, fertility, and risks, she was offered the choice between a hysterectomy (surgical removal of the uterus) or uterine artery embolization.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+A
+
+56.3 mm
+
+
+
+A uterine artery embolization is a procedure where an interventional radiologist uses a catheter to inject small particles into the uterine arteries. This reduces the blood supply to the fibroids and causes them to shrink.
+
+The patient opted for the uterine artery embolization.
+
+An MRI performed 6 months after the embolization procedure showed a favorable reduction in the size of the uterine fibroids (eFig. 5.89).
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+B
+
+46.1 mm
+
+
+eFig. 5.89  Sagittal MRI of the pelvic cavity. A. Measurement of a fibroid before the uterine artery embolization. B. Measurement of a fibroid 6 months after the embolization. The size of the fibroid has decreased.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+524.e5
+
+
+
+
+Arteries	592 Veins      595 Nerves      595 Knee joint      598
+Tibiofibular joint	609 Popliteal fossa      609
+Leg	612
+Bones      612 Joints      614
+Posterior compartment of leg	615 Lateral compartment of leg      622 Anterior compartment of leg      624
+Foot	627
+Bones      629 Joints      633
+Tarsal tunnel, retinacula, and arrangement of major structures at the ankle	642
+Arches of the foot	644 Plantar aponeurosis      645 Fibrous sheaths of toes	645 Extensor hoods      646 Intrinsic muscles      646
+
+Arteries	653 Veins      655 Nerves      655
+
+Surface anatomy	659
+Lower limb surface anatomy	659 Avoiding the sciatic nerve      659
+Finding the femoral artery in the femoral triangle	660
+Identifying structures around the knee	660 Visualizing the contents of the popliteal fossa	662 Finding the tarsal tunnel—the gateway to the
+foot	663
+Identifying tendons around the ankle and in the foot	664
+Finding the dorsalis pedis artery	665 Approximating the position of the plantar arterial
+arch	665
+Major superficial veins	666 Pulse points	667
+
+Clinical cases	668
+Conceptual Overview  •  General Introduction	6
+
+
+
+Conceptual overview GENERAL INTRODUCTION
+
+The lower limb is directly anchored to the axial skeleton by a sacroiliac joint and by strong ligaments, which link the pelvic bone to the sacrum. It is separated from the abdomen, back, and perineum by a continuous line (Fig. 6.1), which:
+
+
+
+iliac spine to separate the lower limb from the anterior and lateral abdominal walls;
+■     passes between the posterior superior iliac spine and along the dorsolateral surface of  the sacrum to the coccyx to separate the lower limb from the muscles of the back; and
+■     joins the medial margin of the sacrotuberous ligament,
+
+
+
+■     joins the pubic tubercle with the anterior superior iliac spine  (position  of  the  inguinal  ligament)  and  then continues along the iliac crest to the posterior superior
+
+
+the ischial tuberosity, the ischiopubic ramus, and the pubic symphysis to separate the lower limb from the perineum.
+
+
+
+
+
+
+
+
+Posterior superior iliac spine	Sacrum
+Sacro-iliac joint Iliac crest
+
+
+
+
+
+Anterior superior iliac spine
+
+Lower limb
+
+Sacrotuberous ligament
+Pubic tubercle
+
+
+Ischiopubic ramus
+
+
+
+
+Fig. 6.1  Upper margin of the lower limb.
+
+
+
+
+
+
+
+
+
+
+
+
+
+527
+Lower Limb
+
+
+
+The lower limb is divided into the gluteal region, thigh, leg, and foot on the basis of major joints, component bones, and superficial landmarks (Fig. 6.2):
+
+■     Anteriorly, the thigh is between the inguinal ligament and the knee joint—the hip joint is just inferior to the middle third of the inguinal ligament, and the posterior thigh is between the gluteal fold and the knee.
+
+■     The gluteal region is posterolateral and between the iliac crest and the fold of skin (gluteal fold) that defines the lower limit of the buttocks.
+
+■     The leg is between the knee and ankle joint. ■     The foot is distal to the ankle joint.
+
+
+
+
+
+
+
+Anterior abdominal wall	Back
+
+
+
+
+
+Anterior superior iliac spine
+
+Inguinal ligament
+
+Iliac crest
+
+
+Gluteal region
+
+
+
+Pubic tubercle
+Anterior thigh
+
+
+Posterior thigh	Gluteal fold
+
+
+
+Knee joint
+
+
+
+
+Leg
+
+
+
+
+Ankle joint
+
+Foot
+
+
+
+Fig. 6.2  Regions of the lower limb.
+
+
+
+
+
+
+
+
+
+528
+Conceptual Overview  •  Function	6
+
+
+
+The femoral triangle and popliteal fossa, as well as the posteromedial side of  the ankle, are important areas of transition through which structures pass between regions (Fig. 6.3).
+The femoral triangle is a pyramid-shaped depression formed by muscles in the proximal regions of  the thigh and by the inguinal ligament, which forms the base of the triangle. The major blood supply and one of the nerves of the limb (femoral nerve) enter into the thigh from the abdomen by passing under the inguinal ligament and into the femoral triangle.
+The popliteal fossa is posterior to the knee joint and is a diamond-shaped region formed by muscles of the thigh and leg. Major vessels and nerves pass between the thigh and leg through the popliteal fossa.
+Most  nerves,  vessels,  and  flexor  tendons  that  pass between the leg and foot pass through a series of canals (collectively termed the tarsal tunnel) on the posteromedial side of the ankle. The canals are formed by adjacent bones and  a  flexor  retinaculum,  which  holds  the  tendons  in position.
+
+
+FUNCTION
+Support the body weight
+A major function of the lower limb is to support the weight of  the body with minimal expenditure of  energy. When standing erect, the center of gravity is anterior to the edge of the SII vertebra in the pelvis (Fig. 6.4). The vertical line through the center of  gravity is slightly posterior to the hip  joints,  anterior  to  the  knee  and  ankle  joints,  and directly over the almost circular support base formed by the feet on the ground and holds the knee and hip joints in extension.
+The organization of ligaments at the hip and knee joints, together with the shape of the articular surfaces, particu-larly at the knee, facilitates “locking” of these joints into position when standing, thereby reducing the muscular energy required to maintain a standing position.
+
+Locomotion
+A second major function of the lower limbs is to move the body through space. This involves the integration of move-ments at all joints in the lower limb to position the foot on the ground and to move the body over the foot.
+
+
+
+
+Inguinal ligament
+
+Femoral triangle
+
+Center of gravity
+posterior to hip joint
+
+
+Center of gravity
+
+Popliteal fossa (posterior to knee)
+
+
+
+Anterior to knee
+
+
+Line of gravity
+
+
+Tarsal tunnel
+
+Anterior to ankle
+
+
+
+Fig. 6.3  Areas of transition.	Fig. 6.4  Center and line of gravity.	529
+Lower Limb
+
+
+
+Movements  at  the  hip  joint  are  flexion,  extension, abduction, adduction, medial and lateral rotation, and circumduction (Fig. 6.5).
+The knee and ankle joints are primarily hinge joints. Movements at the knee are mainly flexion and extension (Fig.  6.6A).  Movements  at  the  ankle  are  dorsiflexion
+
+(movement of the dorsal side of the foot toward the leg) and plantarflexion (Fig. 6.6B).
+During walking, many anatomical features of the lower limbs contribute to minimizing fluctuations in the body’s center of gravity and thereby reduce the amount of energy needed to maintain locomotion and produce a smooth,
+
+
+
+
+
+
+Abduction of
+femur on fixed pelvis
+
+Gluteus medius
+and gluteus minimus
+
+Abduction of pelvis on fixed femur
+
+
+
+
+Abduction
+
+Extension	Flexion
+
+Adduction
+
+
+
+
+
+
+
+A	B
+
+
+
+
+
+
+
+Internal rotation
+
+
+External rotation
+
+
+
+
+
+
+
+
+
+
+Extension
+
+Flexion	Abduction
+C	D	Adduction
+
+Fig. 6.5  Movements of the hip joint. A. Flexion and extension. B. Abduction and adduction. C. External and internal rotation. D. Circumduction.
+
+
+530
+Conceptual Overview  •  Component Parts	6
+
+
+
+
+
+
+
+
+
+
+
+
+Flexion
+
+
+Dorsiflexion Extension
+
+
+
+A	B
+Plantarflexion
+
+Fig. 6.6  Movements of the knee and ankle. A. Knee flexion and extension. B. Ankle dorsiflexion and plantarflexion.
+
+
+
+
+
+
+efficient  gait  (Fig.  6.7). They  include  pelvic  tilt  in  the coronal  plane,  pelvic  rotation  in  the  transverse  plane, movement of the knees toward the midline, flexion of the knees, and complex interactions between the hip, knee, and ankle. As a result, during walking, the body’s center
+
+Although the main movements at the knee are flexion and extension, the knee joint also allows the femur to rotate on the tibia. This rotation contributes to “locking” of the knee when fully extended, particularly when standing.
+The leg contains two bones:
+
+
+
+of gravity normally fluctuates only 5 cm in both vertical and lateral directions.
+
+COMPONENT PARTS Bones and joints
+The bones of the gluteal region and the thigh are the pelvic bone and the femur (Fig. 6.8). The large ball and socket joint between these two bones is the hip joint.
+The femur is the bone of the thigh. At its distal end, its
+
+
+■     The tibia is medial in position, is larger than the laterally positioned fibula, and is the weight-bearing bone.
+■     The fibula does not take part in the knee joint and forms only the most lateral part of  the ankle joint— proximally, it forms a small synovial joint (superior tib-iofibular joint) with the inferolateral surface of the head of the tibia.
+
+The tibia and fibula are linked along their lengths by an
+
+
+
+major weight-bearing articulation is with the tibia, but it also articulates anteriorly with the patella (knee cap). The patella is the largest sesamoid bone in the body and is embedded in the quadriceps femoris tendon.
+The joint between the femur and tibia is the principal
+
+interosseous  membrane,  and  at  their  distal  ends  by  a fibrous  inferior  tibiofibular  joint,  and  little  movement occurs between them. The distal surfaces of the tibia and fibula together form a deep recess. The ankle joint is formed by this recess and part of one of the tarsal bones of the foot
+
+articulation  of  the  knee  joint,  but  the  joint  between	(talus), which projects into the recess. The ankle is most the patella and femur shares the same articular cavity.	stable when dorsiflexed.
+
+
+
+
+
+531
+Lower Limb
+
+
+
+
+
+Vertical shift in center of gravity
+
+
+
+
+
+
+
+Pelvic rotation in transverse plane minimizes drop in center of gravity by effectively lengthening the limbs
+
+Movement of knees toward midline (adduction of hip) minimizes lateral shift in center of gravity
+
+
+
+
+
+With adduction of hip (knees move toward midline)
+
+
+
+
+External rotation of hip joint
+
+
+Internal rotation of hip joint
+
+
+
+
+Knee flexion on full stance. Limb minimizes rise in center of gravity by effectively shortening the limb
+
+
+Center of gravity with knee not flexed
+Center of gravity with knee flexed
+
+No adduction
+of hip (knees do not move toward midline)
+
+
+Lateral shift in center of gravity
+
+
+Pelvic tilt (drop) on swing side minimizes rise in center of gravity
+
+
+
+Abduction on stance side controls and limits the drop
+
+
+
+
+
+Flexion
+
+
+
+
+
+
+
+
+Fig. 6.7  Some of the determinants of gait.
+
+
+532
+Conceptual Overview  •  Component Parts	6
+
+
+
+
+
+
+Pelvic bone
+
+Hip joint
+
+
+
+
+
+
+
+
+
+Femur
+
+
+
+
+
+
+
+
+
+Knee joint	Patella
+
+
+
+
+
+Tibia
+
+
+
+Fibula
+
+
+
+
+
+
+Medial malleolus Lateral malleolus
+
+
+Ankle joint
+
+
+
+
+Fig. 6.8  Bones and joints of the lower limb.
+
+
+
+533
+Lower Limb
+
+
+The bones of the foot consist of the tarsal bones, the	Independent   movements   of	the   metatarsals   are
+
+metatarsals, and the phalanges (Fig. 6.9). There are seven tarsal bones, which are organized in two rows with an intermediate bone between the two rows on the medial side. Inversion and eversion of the foot, or turning the sole of the foot inward and outward, respectively, occur at joints between the tarsal bones.
+The  tarsal  bones  articulate  with  the  metatarsals  at tarsometatarsal joints, which allow only limited sliding movements.
+
+restricted by deep transverse metatarsal ligaments, which effectively link together the distal heads of the bones at the metatarsophalangeal joints. There is a metatarsal for each of the five digits, and each digit has three phalanges except for the great toe (digit I), which has only two.
+The metatarsophalangeal joints allow flexion, exten-sion, abduction, and adduction of the digits, but the range of movement is more restricted than in the hand.
+
+
+
+
+
+
+Toes
+
+I	II
+
+III
+
+Phalanges	IV
+
+V
+
+
+
+
+
+
+Deep transverse Metatarsals	metatarsal ligaments
+
+
+
+
+
+
+Cuneiforms
+Distal
+row	Cuboid
+
+Medial Intermediate Lateral
+
+
+
+Intermediate Tarsal bones	bone
+
+Navicular
+
+Talus
+
+
+
+Proximal row
+
+Subtalar joint
+
+Articular surface for ankle joint
+
+
+
+Calcaneus
+
+
+
+534	Fig. 6.9  Bones of the foot.
+Conceptual Overview  •  Component Parts	6
+
+
+
+
+Lateral malleolus
+
+
+
+
+
+
+Medial malleolus
+
+
+
+Lateral arch
+
+
+
+
+Medial arch
+
+Plantar calcaneonavicular ligament
+
+Talus	Calcaneus
+
+II	III
+I	IV
+Transverse arch	V through metatarsals
+
+
+Fig. 6.10  Longitudinal and transverse arches of the foot.
+
+
+
+
+
+
+The interphalangeal joints are hinge joints and allow flexion and extension.
+The bones of the foot are not organized in a single plane so that they lie flat on the ground. Rather, the metatarsals and tarsals form longitudinal and transverse arches (Fig. 6.10). The longitudinal arch is highest on the medial side of the foot. The arches are flexible in nature and are sup-ported by muscles and ligaments. They absorb and transmit forces during walking and standing.
+
+Muscles
+Muscles of  the gluteal region consist predominantly of extensors, rotators, and abductors of  the hip joint (Fig. 6.11). In addition to moving the thigh on a fixed pelvis, these muscles also control the movement of the pelvis rela-tive to the limb bearing the body’s weight (weight-bearing or stance limb) while the other limb swings forward (swing limb) during walking.
+
+
+
+
+Extensor
+(gluteus maximus)
+
+
+Abductors (gluteus medius
+and gluteus minimus)
+
+
+Rotators
+(piriformis, obturator internus, gemelli, quadratus femoris)
+
+
+
+
+
+
+
+
+
+Fig. 6.11  Muscles of the gluteal region.	535
+Lower Limb
+
+
+
+Major flexor muscles of the hip (iliopsoas—psoas major and iliacus) do not originate in the gluteal region or the
+
+Muscles in the leg are divided into lateral (fibular), anterior, and posterior compartments:
+
+
+
+thigh. Instead, they are attached to the posterior abdominal wall and descend through the gap between the inguinal ligament and pelvic bone to attach to the proximal end of the femur (Fig. 6.12).
+Muscles in the thigh and leg are separated into three compartments by layers of  fascia, bones, and ligaments (Fig. 6.13).
+In  the  thigh,  there  are  medial  (adductor),  anterior (extensor), and posterior (flexor) compartments:
+
+
+■     Muscles  in  the  lateral  compartment  predominantly evert the foot.
+■     Muscles in the anterior compartment dorsiflex the foot and extend the digits.
+■     Muscles in the posterior compartment plantarflex the foot and flex the digits; one of the muscles can also flex the knee because it attaches superiorly to the femur.
+
+Specific muscles in each of the three compartments in
+
+
+
+■     Most muscles in the medial compartment act mainly on the hip joint.
+■     The large muscles (hamstrings) in the posterior com-partment act on the hip (extension) and knee (flexion) because they attach to both the pelvis and bones of the leg.
+
+the leg also provide dynamic support for the arches of the foot.
+Muscles found entirely in the foot (intrinsic muscles) modify the forces produced by tendons entering the toes from the leg and provide dynamic support for the longitu-dinal arches of the foot when walking, particularly when
+
+■     Muscles  in  the  anterior  compartment  (quadriceps	levering the body forward on the stance limb just before femoris) predominantly extend the knee.	toe-off.
+
+
+
+
+
+
+Anterior compartment
+
+
+
+Psoas major
+
+
+Iliacus
+
+
+Hip flexors (iliopsoas)
+
+
+
+Femur
+
+
+Inguinal ligament                                                               Posterior compartment
+
+
+Medial compartment
+
+Anterior compartment
+
+
+
+
+
+Lateral compartment
+
+
+
+
+
+Fig. 6.12  Major flexors of the hip.
+
+536
+
+Posterior compartment
+
+Fig. 6.13  Muscle compartments in the thigh and leg.
+Conceptual Overview  •  Key Points	6
+
+
+
+RELATIONSHIP TO OTHER REGIONS
+
+Unlike  in  the  upper  limb  where  most  structures  pass between the neck and limb through a single axillary inlet, in the lower limb, there are four major entry and exit points between the lower limb and the abdomen, pelvis, and perineum (Fig. 6.14). These are:
+
+This gap between the pelvic bone and the inguinal liga-ment is a weak area in the abdominal wall and often associ-ated with abnormal protrusion of  the abdominal cavity and contents into the thigh (femoral hernia). This type of hernia usually occurs where the lymphatic vessels pass through the gap (the femoral canal).
+
+
+
+■     the gap between the inguinal ligament and pelvic bone, ■     the greater sciatic foramen,
+■     the obturator canal (at the top of the obturator foramen), and
+■     the lesser sciatic foramen.
+
+Pelvis
+Structures within the pelvis communicate with the lower limb through two major apertures (Fig. 6.14).
+Posteriorly, structures communicate with the gluteal region through the greater sciatic foramen and include:
+
+
+
+Abdomen
+The lower limb communicates directly with the abdomen through a gap between the pelvic bone and the inguinal ligament (Fig. 6.14). Structures passing though this gap include:
+
+
+■     a muscle—piriformis;
+■     nerves—sciatic,  superior  and  inferior  gluteal,  and pudendal nerves; and
+■     vessels—superior and inferior gluteal arteries and veins, and the internal pudendal artery.
+
+
+
+■     muscles—psoas major, iliacus, and pectineus;
+■     nerves—femoral and femoral branch of the genitofemo-ral nerves, and the lateral cutaneous nerve of the thigh;
+■     vessels—femoral artery and vein; and ■     lymphatics.
+
+The sciatic nerve is the largest peripheral nerve of the body and is the major nerve of the lower limb.
+Anteriorly, the obturator nerve and vessels pass between the pelvis and thigh through the obturator canal. This canal is formed between bone at the top of the obturator foramen and the obturator membrane, which closes most of the foramen during life.
+
+
+
+
+
+Greater sciatic foramen
+Inguinal ligament
+
+
+Sacrotuberous ligament
+Sacrospinous ligament
+
+Perineum
+Structures pass between the perineum and gluteal region through the lesser sciatic foramen (Fig. 6.14). The most important with respect to the lower limb is the tendon of the obturator internus muscle.
+The nerve and artery of  the perineum (the internal pudendal artery and pudendal nerve) pass out of the pelvis through the greater sciatic foramen into the gluteal region and then immediately pass around the ischial spine and sacrospinous  ligament  and  through  the  lesser  sciatic foramen to enter the perineum.
+
+
+
+KEY POINTS
+Innervation is by lumbar and sacral Obturator canal	spinal nerves
+
+Obturator membrane
+
+Lesser sciatic foramen	  Gap between inguinal ligament and pelvic bone
+
+Somatic motor and general sensory innervation of  the lower limb is by peripheral nerves emanating from the lumbar and sacral plexuses on the posterior abdominal and pelvic walls. These plexuses are formed by the anterior
+
+Fig. 6.14  Apertures of communication between the lower limb and other regions.
+
+
+rami of L1 to L3 and most of L4 (lumbar plexus) and L4 to
+S5 (sacral plexus).	537
+Lower Limb
+
+
+
+Nerves originating from the lumbar and sacral plexuses and entering the lower limb carry fibers from spinal cord levels L1 to S3 (Fig. 6.15). Nerves from lower sacral seg-ments innervate the perineum. Terminal nerves exit the abdomen and pelvis through a number of apertures and foramina and enter the limb. As a consequence of  this innervation, lumbar and upper sacral nerves are tested
+
+
+
+Lumbar
+
+
+Ilio-inguinal (L1)
+
+clinically by examining the lower limb. In addition, clinical signs (such as pain, pins-and-needles sensations, paresthe-sia, and fascicular muscle twitching) resulting from any disorder  affecting  these  spinal  nerves  (e.g.,  herniated intervertebral disc in the lumbar region) appear in the lower limb.
+
+
+
+
+Sacral
+
+Superior gluteal nerve (L4 to S1)
+
+
+
+Iliohypogastric (L1)
+
+
+Genitofemoral (L1, L2)
+Lateral cutaneous nerve of thigh (L2, L3)
+
+Sacrospinous ligament
+
+LI
+
+LII
+LIII	Sciatic nerve (L4 to S3)
+
+LIV
+
+LV
+
+Inferior gluteal nerve (L5 to S2)
+
+
+
+Femoral nerve (L2 to L4)	Pudendal nerve (S2 to S4)
+
+
+Obturator nerve (L2 to L4)
+
+
+
+
+
+
+
+
+Tibial nerve (branch of sciatic) (L4 to S3)
+
+
+
+Common fibular nerve (branch of sciatic) (L4 to S2)
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+538	Fig. 6.15  Innervation of the lower limb.
+Conceptual Overview  •  Key Points	6
+
+
+
+Dermatomes in the lower limb are shown in Fig. 6.16. Regions that can be tested for sensation and are reasonably autonomous (have minimal overlap) are:
+
+■     Flexion of the hip is controlled primarily by L1 and L2. ■     Extension of the knee is controlled mainly by L3 and L4. ■     Knee flexion is controlled mainly by L5 to S2.
+
+
+■     over the inguinal ligament—L1, ■     lateral side of the thigh—L2,
+■     lower medial side of the thigh—L3,
+
+■     Plantarflexion of the foot is controlled predominantly by S1 and S2.
+■     Adduction of the digits is controlled by S2 and S3.
+
+
+
+■     medial side of the great toe (digit I)—L4, ■     medial side of digit II—L5,
+■     little toe (digit V)—S1,
+■     back of the thigh—S2, and
+
+
+In an unconscious patient, both somatic sensory and somatic motor functions of spinal cord levels can be tested using tendon reflexes:
+
+
+
+■     skin over the gluteal fold—S3.
+
+The dermatomes of S4 and S5 are tested in the perineum. Selected joint movements are used to test myotomes
+
+
+■     A tap on the patellar ligament at the knee tests predomi-nantly L3 and L4.
+■     A  tendon  tap  on  the  calcaneal  tendon  posterior  to the ankle (tendon of gastrocnemius and soleus) tests S1
+
+(Fig. 6.17). For example:	and S2.
+
+
+
+Adduction of toes S2, S3
+
+
+L1	L2
+
+L1	S3
+
+S4
+
+L2
+L2	L1, L2
+
+L3
+S2	L3, L4
+
+L3
+S2	L3	L5 to S2
+
+
+
+
+
+
+L4
+L5
+L5
+
+S1, S2 L4
+Fig. 6.17  Movements generated by myotomes.
+
+
+
+
+
+S1
+S1
+
+L4	S1
+L5
+
+L4
+L5
+
+Fig. 6.16  Dermatomes of the lower limb. Dots indicate
+autonomous zones (i.e., with minimal overlap).	539
+Lower Limb
+
+
+
+Each of the major muscle groups or compartments in the lower limb is innervated primarily by one or more of the major nerves that originate from the lumbar and sacral plexuses (Fig. 6.18):
+
+■     Most muscles in the anterior compartment of the thigh are innervated by the femoral nerve (except the tensor fasciae  latae,  which  are  innervated  by  the  superior gluteal nerve).
+■     Most muscles in the medial compartment are innervated
+
+
+
+■     Large muscles in the gluteal region are innervated by the superior and inferior gluteal nerves.
+
+
+
+
+Femoral nerve (anterior compartment of thigh)
+
+Superior and inferior gluteal nerves
+
+Obturator
+(medial compartment of thigh)
+
+mainly by the obturator nerve (except the pectineus, which is innervated by the femoral nerve, and part of the adductor magnus, which is innervated by the tibial division of the sciatic nerve).
+■     Most muscles in the posterior compartment of the thigh and the leg and in the sole of the foot are innervated by the tibial part of the sciatic nerve (except the short head of  the biceps femoris in the posterior thigh, which is innervated by the common fibular division of the sciatic nerve).
+■     The anterior and lateral compartments of the leg and muscles associated with the dorsal surface of the foot are innervated by the common fibular part of the sciatic
+
+
+
+
+Sciatic nerve (posterior compartment of thigh, leg, and
+sole of foot)
+
+
+
+Common fibular nerve
+
+nerve.
+
+In addition to innervating major muscle groups, each of the major peripheral nerves originating from the lumbar and sacral plexuses carries general sensory information from patches of  skin (Fig. 6.19). Sensation from these areas can be used to test for peripheral nerve lesions:
+
+
+
+
+
+
+
+Superficial branch
+(lateral compartment of leg)
+
+Deep branch
+(anterior compartment of leg)
+
+■     The femoral nerve innervates skin on the anterior thigh, medial side of the leg, and medial side of the ankle.
+■     The obturator nerve innervates the medial side of the thigh.
+■     The tibial part of the sciatic nerve innervates the lateral side of the ankle and foot.
+■     The common fibular nerve innervates the lateral side of the leg and the dorsum of the foot.
+
+
+
+
+
+Fig. 6.18  Major nerves of the lower limb (colors indicate regions of motor innervation).
+
+
+
+
+
+
+
+
+
+
+
+
+
+540
+Conceptual Overview  •  Key Points	6
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Posterior rami (L1 to L3)
+
+
+Posterior rami (S1 to S3)
+
+
+
+
+Obturator nerve
+
+
+Femoral nerve (anterior cutaneous nerves of thigh)
+
+
+
+
+
+Femoral nerve (saphenous nerve)
+
+Lateral cutaneous nerve of thigh
+(from lumbar plexus)
+
+Posterior cutaneous nerve of thigh
+(from sacral plexus)
+
+
+
+
+Common fibular nerve (lateral cutaneous of calf)
+
+
+
+
+
+Obturator nerve
+
+
+
+
+
+
+Femoral nerve (saphenous nerve)
+
+
+
+
+
+Common fibular nerve	Tibial nerve (sural nerve) (superficial branch)
+
+
+
+Common fibular nerve (deep branch)
+
+Medial plantar nerve
+
+
+Tibial nerve (sural nerve)
+
+Lateral plantar nerve
+
+
+Tibial nerve (medial calcaneal branches)
+
+
+Fig. 6.19  Regions of skin innervated by peripheral nerves.
+
+
+
+
+
+
+
+
+
+
+
+
+541
+Lower Limb
+
+
+
+
+Nerves related to bone
+The common fibular branch of  the sciatic nerve curves laterally around the neck of the fibula when passing from the popliteal fossa into the leg (Fig. 6.20). The nerve can
+
+The most important superficial veins are the great and small saphenous veins, which originate from the medial and lateral sides, respectively, of a dorsal venous arch in the foot.
+
+
+
+be rolled against bone just distal to the attachment of biceps femoris to the head of the fibula. In this location, the nerve can be damaged by impact injuries, fractures to the bone, or leg casts that are placed too high.
+
+Superficial veins
+Large veins embedded in the subcutaneous (superficial) fascia of the lower limb (Fig. 6.21) often become distended (varicose). These vessels can also be used for vascular transplantation.
+
+■     The great saphenous vein passes up the medial side of the leg, knee, and thigh to pass through an opening in deep fascia covering the femoral triangle and join with the femoral vein.
+■     The small saphenous vein passes behind the distal end of the fibula (lateral malleolus) and up the back of the leg to penetrate deep fascia and join the popliteal vein posterior to the knee.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Great saphenous vein
+
+Common fibular nerve (neck of fibula)
+
+
+
+Superficial branch
+
+
+Small saphenous vein
+Deep branch
+
+
+
+
+
+
+Lateral malleolus
+
+
+Lateral marginal vein
+
+Medial malleolus
+
+
+Medial marginal vein
+
+
+Dorsal venous arch
+
+
+Fig. 6.21  Superficial veins.
+
+542	Fig. 6.20  Nerves related to bone.
+Regional Anatomy  •  Bony Pelvis	6
+
+
+Regional anatomy Bony pelvis
+The external surfaces of  the pelvic bones, sacrum, and coccyx are predominantly the regions of the pelvis associ-ated with the lower limb, although some muscles do origi-nate from the deep or internal surfaces of  these bones and from the deep surfaces of the lumbar vertebrae, above (Fig. 6.22).
+Each  pelvic  bone  is  formed  by  three  bones  (ilium, ischium, and pubis), which fuse during childhood. The ilium is superior and the pubis and ischium are antero-inferior and posteroinferior, respectively.
+The ilium articulates with the sacrum. The pelvic bone is further anchored to the end of  the vertebral column (sacrum and coccyx) by the sacrotuberous and sacrospi-nous ligaments, which attach to a tuberosity and spine on the ischium.
+
+
+
+
+
+The outer surface of the ilium, and the adjacent surfaces of  the sacrum, coccyx, and sacrotuberous ligament are associated with the gluteal region of the lower limb and provide extensive muscle attachment. The ischial tuberos-ity provides attachment for many of  the muscles in the posterior compartment of the thigh, and the ischiopubic ramus and body of the pubis are associated mainly with muscles in the medial compartment of the thigh. The head of the femur articulates with the acetabulum on the lateral surface of the pelvic bone.
+
+Ilium
+The upper fan-shaped part of the ilium is associated on its inner side with the abdomen and on its outer side with the lower limb. The top of this region is the iliac crest, which
+
+
+
+
+
+
+
+
+
+
+
+
+
+Tuberculum of iliac crest
+
+
+
+
+
+Anterior abdominal wall Iliac crest
+
+Anterior superior iliac spine
+
+Inguinal ligament
+
+Anterior inferior iliac spine
+
+Iliopubic eminence
+
+Horizontal plane through top of iliac crest LIV spine
+Ilium
+Anterior gluteal line
+Posterior gluteal line Posterior superior iliac spine
+
+Sacrum
+Posterior inferior iliac spine Inferior gluteal line
+
+
+Pubic tubercle		Sacrotuberous ligament Pubis
+
+
+Acetabulum
+Ischium
+
+Sacrospinous ligament
+
+Ischial spine
+
+Ischial tuberosity
+
+
+Fig. 6.22  External surface of the bony pelvis. Lateral view.
+
+
+543
+Lower Limb
+
+
+
+ends anteriorly as the anterior superior iliac spine and posteriorly  as  the  posterior  superior  iliac  spine.  A prominent lateral expansion of the crest just posterior to the anterior superior iliac spine is the tuberculum of the iliac crest.
+The anterior inferior iliac spine is on the anterior margin of the ilium, and below this, where the ilium fuses with the
+
+■     The posterior gluteal line descends almost vertically from the iliac crest to a position near the posterior inferior iliac spine—the gluteus medius muscle attaches to bone between the anterior and posterior gluteal lines, and the gluteus maximus muscle attaches posterior to the posterior gluteal line.
+
+pubis, is a raised area of bone (the iliopubic eminence). The gluteal surface of the ilium faces posterolaterally and lies below the iliac crest. It is marked by three curved lines (inferior, anterior, and posterior gluteal lines), which
+divide the surface into four regions:
+
+
+Ischial tuberosity
+The ischial tuberosity is posteroinferior to the acetabu-lum and is associated mainly with the hamstring muscles of the posterior thigh (Fig. 6.23). It is divided into upper and lower areas by a transverse line.
+
+
+
+■     The inferior gluteal line originates just superior to the anterior inferior iliac spine and curves inferiorly across the  bone  to  end  near  the  posterior  margin  of  the acetabulum—the rectus femoris muscle attaches to the
+
+The upper area of the ischial tuberosity is oriented verti-cally and is further subdivided into two parts by an oblique line, which descends, from medial to lateral, across the surface:
+
+
+
+anterior inferior iliac spine and to a roughened patch of bone between the superior margin of the acetabulum and the inferior gluteal line.
+■     The anterior gluteal line originates from the lateral margin of the iliac crest between the anterior superior iliac spine and the tuberculum of  the iliac crest, and arches  inferiorly  across  the  ilium  to  disappear  just superior  to  the  upper  margin  of  the  greater  sciatic
+
+
+■     The more medial part of the upper area is for the attach-ment of  the combined origin of  the semitendinosus muscle and the long head of the biceps femoris muscle.
+■     The lateral part is for the attachment of the semimem-branosus muscle.
+
+The lower area of the ischial tuberosity is oriented hori-
+
+
+
+foramen—the gluteus minimus muscle originates from between the inferior and anterior gluteal lines.
+
+zontally and is divided into medial and lateral regions by a ridge of bone:
+
+
+
+
+
+
+
+
+
+
+
+
+
+Acetabulum
+
+Ischial spine
+
+Body of pubic bone
+
+
+Ischiopubic ramus
+
+Obturator foramen
+
+
+
+For attachment of adductor magnus muscle
+
+For attachment of semimembranosus muscle
+
+For attachment of semitendinosus and long head of biceps femoris muscle
+
+For attachment of sacrotuberous ligament
+
+Covered by connective tissue and bursa
+
+
+544	Fig. 6.23  Ischial tuberosity. Posterolateral view.
+Regional Anatomy  •  Bony Pelvis	6
+
+
+
+■     The lateral region provides attachment for part of the adductor magnus muscle.
+■     The medial part faces inferiorly and is covered by con-nective tissue and by a bursa.
+
+■     The  articular  surface  is  broad  and  surrounds  the anterior, superior, and posterior margins of the acetabu-lar fossa.
+
+The  smooth  crescent-shaped  articular  surface  (the
+
+
+
+When sitting, this medial part supports the body weight. The sacrotuberous ligament is attached to a sharp ridge
+on the medial margin of the ischial tuberosity.
+
+Ischiopubic ramus and pubic bone
+The external surfaces of the ischiopubic ramus anterior to the ischial tuberosity and the body of  the pubis provide attachment for muscles of the medial compartment of the thigh  (Fig.  6.23). These  muscles  include  the  adductor longus, adductor brevis, adductor magnus, pectineus, and gracilis.
+
+Acetabulum
+The large cup-shaped acetabulum for articulation with the head of the femur is on the lateral surface of the pelvic bone in the region where the ilium, pubis, and ischium fuse
+
+lunate  surface) is broadest superiorly where most of the body’s weight is transmitted through the pelvis to the femur. The lunate surface is deficient inferiorly at the ace-tabular notch.
+The acetabular fossa provides attachment for the liga-ment of the head of the femur, whereas blood vessels and nerves pass through the acetabular notch.
+
+
+
+
+
+
+Ilium
+
+
+Lunate surface (articular)
+
+
+
+(Fig. 6.24).
+The margin of the acetabulum is marked inferiorly by a prominent notch (acetabular notch).
+The wall of  the acetabulum consists of  nonarticular and articular parts:
+
+
+Pubis
+
+
+
+
+Acetabular notch
+
+
+Acetabular fossa
+
+
+
+■     The nonarticular part is rough and forms a shallow circular depression (the acetabular fossa) in central and inferior parts of the acetabular floor—the acetabu-lar notch is continuous with the acetabular fossa.
+
+
+Ischium
+
+Fig. 6.24  Acetabulum.
+
+
+
+
+
+
+
+In the clinic
+
+Pelvic fractures
+The pelvic bones, sacrum, and associated joints form a bony ring surrounding the pelvic cavity. Soft tissue and visceral organ damage must be suspected when the pelvis is fractured. Patients with multiple injuries and evidence of chest, abdominal, and lower limb trauma should also be investigated for pelvic trauma.
+Pelvic fractures can be associated with appreciable blood loss (concealed exsanguination) and blood transfusion is often required. In addition, this bleeding tends to form
+a significant pelvic hematoma, which can compress nerves, press on organs, and inhibit pelvic visceral function (Fig. 6.25).
+There are many ways of classifying pelvic fractures, which enable the surgeon to determine the appropriate
+
+
+
+treatment and the patient’s prognosis. Pelvic fractures are generally of four types.
+
+■     Type 1 injuries occur without disruption of the bony pelvic ring (e.g., a fracture of the iliac crest). These types of injuries are unlikely to represent significant trauma, though in the case of a fracture of the iliac crest, blood loss needs to be assessed.
+■     Type 2 injuries occur with a single break in the bony pelvic ring. An example of this would be a single fracture with diastasis (separation) of the symphysis pubis. Again, these injuries are relatively benign in nature, but it may be appropriate to assess for blood loss.
+(continues)
+
+545
+Lower Limb
+
+
+In the clinic—cont’d
+
+■     Type 3 injuries occur with double breaks in the bony	Bladder	Hematoma pelvic ring. These include bilateral fractures of the pubic
+rami, which may produce urethral damage.
+■     Type 4 injuries occur at and around the acetabulum.
+
+Other types of pelvic ring injuries include fractures of the pubic rami and disruption of the sacro-iliac joint with or without dislocation. This may involve significant visceral pelvic trauma and hemorrhage.
+Other general pelvic injuries include stress fractures and insufficiency fractures, as seen in athletes and elderly patients with osteoporosis, respectively.
+
+
+
+
+
+
+
+Fractures
+
+Fig. 6.25  Multiple fractures of the pelvis. Radiograph with contrast in the bladder. A large accumulation of blood is deforming the bladder.
+
+
+
+
+Proximal femur
+The  femur  is  the  bone  of  the  thigh  and  the  longest bone in the body. Its proximal end is characterized by
+
+
+distinct oval depression for attachment of  the obturator externus muscle.
+The greater trochanter has an elongate ridge on its
+
+a head and neck, and two large projections (the greater	anterolateral  surface  for  attachment  of   the  gluteus
+
+and lesser trochanters) on the upper part of  the shaft (Fig. 6.26).
+The head of the femur is spherical and articulates with the acetabulum of the pelvic bone. It is characterized by a nonarticular  pit  (fovea)  on  its  medial  surface  for  the attachment of the ligament of the head.
+The neck of the femur is a cylindrical strut of bone that connects the head to the shaft of  the femur. It projects superomedially from the shaft at an angle of approximately 125°, and projects slightly forward. The orientation of the neck relative to the shaft increases the range of movement of the hip joint.
+The upper part of the shaft of the femur bears a greater and  lesser  trochanter,  which  are  attachment  sites  for muscles that move the hip joint.
+
+Greater and lesser trochanters
+The greater trochanter extends superiorly from the shaft of the femur just lateral to the region where the shaft joins the neck of the femur (Fig. 6.26). It continues posteriorly where its medial surface is deeply grooved to form the
+546	trochanteric fossa. The lateral wall of this fossa bears a
+
+minimus and a similar ridge more posteriorly on its lateral surface for attachment of  the gluteus medius. Between these two points, the greater trochanter is palpable.
+On the medial side of the superior aspect of the greater trochanter and just above the trochanteric fossa is a small impression for attachment of the obturator internus and its associated gemelli muscles, and immediately above and behind this feature is an impression on the margin of the trochanter for attachment of the piriformis muscle.
+The  lesser  trochanter  is  smaller  than  the  greater trochanter and has a blunt conical shape. It projects pos-teromedially from the shaft of the femur just inferior to the junction with the neck (Fig. 6.26). It is the attachment site for  the  combined  tendons  of  psoas  major  and  iliacus muscles.
+Extending between the two trochanters and separating the shaft from the neck of the femur are the intertrochan-teric line and intertrochanteric crest.
+
+Intertrochanteric line
+The intertrochanteric line is a ridge of  bone on the anterior surface of  the upper margin of  the shaft that
+Regional Anatomy  •  Proximal Femur	6
+
+
+
+Neck Trochanteric fossa
+Attachment site for piriformis muscle
+
+Greater trochanter
+
+
+
+
+Head
+
+Tubercle
+
+
+Fovea	Piriformis
+Greater trochanter
+
+Attachment of gluteus medius
+
+
+
+
+Attachment site for gluteus minimus
+
+
+Neck
+Intertrochanteric
+line                  Oval depression for obturator externus
+Lesser trochanter
+End of intertrochanteric line
+
+Obturator internus
+
+Trochanteric fossa
+
+
+Quadrate tubercle
+
+Lesser trochanter
+
+
+
+
+
+Pectineal line (spiral line)
+
+Shaft
+
+
+
+
+
+
+
+A	B
+
+Neck	Gluteus minimus
+
+Greater trochanter Fovea
+Gluteus medius
+
+Attachment site for gluteus medius
+
+Quadrate tubercle
+
+Intertrochanteric crest
+
+Lesser trochanter
+Lesser trochanter
+
+Gluteal tuberosity
+
+Pectineal line (spiral line)
+
+
+
+
+
+
+Medial margin of linea aspera
+
+Linea aspera
+
+C
+
+
+
+Lateral margin of linea aspera
+
+
+D
+
+547 Fig. 6.26  Proximal end of the femur (right). A. Anterior view. B. Medial view. C. Posterior view. D. Lateral view.
+Lower Limb
+
+
+
+descends medially from a tubercle on the anterior surface of  the base of  the greater trochanter to a position just anterior to the base of the lesser trochanter (Fig. 6.26). It is continuous with the pectineal line (spiral line), which curves medially under the lesser trochanter and around the shaft of the femur to merge with the medial margin of the linea aspera on the posterior aspect of the femur.
+
+Intertrochanteric crest
+The intertrochanteric crest is on the posterior surface
+
+The middle third of the shaft of the femur is triangular in shape with smooth lateral and medial margins between anterior, lateral (posterolateral), and medial (posterome-dial) surfaces. The posterior margin is broad and forms a prominent raised crest (the linea aspera).
+The linea aspera is a major site of muscle attachment in the thigh. In the proximal third of the femur, the medial and lateral margins of the linea aspera diverge and con-tinue superiorly as the pectineal line and gluteal tuberosity, respectively (Fig. 6.27):
+
+
+
+of the femur and descends medially across the bone from the posterior margin of the greater trochanter to the base of the lesser trochanter (Fig. 6.26). It is a broad smooth ridge of  bone with a prominent tubercle (the quadrate tubercle) on its upper half, which provides attachment for the quadratus femoris muscle.
+
+
+■     The pectineal line curves anteriorly under the lesser trochanter and joins the intertrochanteric line.
+■     The gluteal tuberosity is a broad linear roughening that curves laterally to the base of the greater trochanter.
+
+
+
+
+Shaft of the femur
+The shaft of the femur descends from lateral to medial in the coronal plane at an angle of 7° from the vertical axis (Fig. 6.27). The distal end of the femur is therefore closer to the midline than the upper end of the shaft.
+
+The gluteus maximus muscle is attached to the gluteal tuberosity.
+The triangular area enclosed by the pectineal line, the gluteal tuberosity, and the intertrochanteric crest is the posterior surface of the proximal end of the femur.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Medial margin
+
+
+Medial
+
+Anterior
+
+Anterior surface
+
+
+
+
+Lateral margin
+
+Lateral
+
+
+Intertrochanteric crest
+Posterior surface of proximal femur
+
+
+
+Medial surface	Lateral surface	Gluteal tuberosity
+
+
+Linea aspera
+
+Posterior
+
+
+Pectineal line (spiral line)
+
+
+
+
+
+
+Linea aspera
+
+
+
+
+548	Fig. 6.27  Shaft of the femur. On the right is a posterior view of proximal shaft of right femur.
+Regional Anatomy  •  Proximal Femur	6
+
+
+In the clinic
+
+Femoral neck fractures
+Femoral neck fractures (Fig. 6.28) can interrupt the blood supply to the femoral head. The blood supply to the head and neck is primarily from an arterial ring formed by the branches of the medial and lateral circumflex femoral arteries around the base of the femoral neck. From here, vessels course along the neck, penetrate the capsule, and supply the femoral head. The blood supply to the femoral head and femoral neck is further enhanced by the artery of the ligamentum teres, a branch of the obturator artery, which is generally small and variable. Femoral neck fractures may disrupt associated vessels and lead to necrosis of the femoral head. Femoral neck fractures can be divided into three categories depending on the location of the fracture line: subcapital (fracture line passes across the femoral head-neck junction), transcervical (fracture line passes through the midportion of the femoral neck), and basicervical (fracture line passes across the base of the neck). Subcapital fractures have the highest risk of developing necrosis of the femoral head, and basicervical fractures have the lowest risk. Elderly patients with osteoporosis tend to have transverse subcapital fractures following low-energy trauma such as a fall from
+a standing height. Conversely, younger patients usually sustain more vertical fractures of the distal femoral neck (basicervical) after high-energy trauma such as a fall from a great height or due to axial load applied to an abducted knee, such as during a motor vehicle accident.
+
+Fractured neck of femur
+
+Fig. 6.28  This radiograph of the pelvis, anteroposterior view, demonstrates a fracture of the neck of the femur.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+549
+Lower Limb
+
+
+
+In the clinic
+
+Intertrochanteric fractures
+In these fractures, the break usually runs from the greater trochanter through to the lesser trochanter and does not involve the femoral neck. Intertrochanteric fractures preserve the femoral neck blood supply and do not render the femoral head ischemic. They are most commonly seen in the elderly and result from low-energy impact (Fig. 6.29).
+Sometimes isolated fractures of the greater or the lesser trochanter can occur. An isolated fracture of the lesser trochanter in adults is most commonly pathological and due to an underlying malignant deposit.
+
+
+
+Intertrochanteric
+fracture
+
+
+
+
+
+
+
+
+
+
+Fig. 6.29  Anteroposterior radiograph showing an intertrochanteric fracture of proximal end of femur.
+
+
+
+
+
+In the clinic
+
+Femoral shaft fractures
+An appreciable amount of energy is needed to fracture the femoral shaft. This type of injury is therefore accompanied by damage to the surrounding soft tissues, which include the muscle compartments and the structures they contain.
+
+in mind. For example, medial and lateral rotation of the femur involves muscles that move the greater trochanter forward and backward, respectively, relative to the acetabu-lum (Fig. 6.30B).
+The articular surfaces of the hip joint are:
+
+■     the spherical head of the femur, and
+
+■     the lunate surface of the acetabulum of the pelvic bone.
+
+
+
+Hip joint
+The hip joint is a synovial articulation between the head of the femur and the acetabulum of  the pelvic bone (Fig. 6.30A). The joint is a multiaxial ball and socket joint designed for stability and weight-bearing at the expense of mobility. Movements at the joint include flexion, extension, abduction, adduction, medial and lateral rotation, and circumduction.
+When considering the effects of muscle action on the hip joint, the long neck of the femur and the angulation of  the neck on the shaft of  the femur must be borne
+
+The acetabulum almost entirely encompasses the hemi-spherical head of the femur and contributes substantially to joint stability. The nonarticular acetabular fossa contains loose connective tissue. The lunate surface is covered by hyaline cartilage and is broadest superiorly.
+Except for the fovea, the head of the femur is also covered by hyaline cartilage.
+The rim of the acetabulum is raised slightly by a fibro-cartilaginous  collar  (the  acetabular  labrum).  Inferiorly, the labrum bridges across the acetabular notch as the transverse acetabular ligament and converts the notch into a foramen (Fig. 6.31A).
+
+
+
+
+
+
+550
+Regional Anatomy  •  Hip Joint	6
+
+
+
+
+
+
+
+
+
+
+
+Acetabulum of pelvic bone
+
+Acetabular labrum
+
+Lateral rotation
+
+
+
+Medial rotation
+
+
+
+
+
+Superior view
+
+
+Head of femur
+
+A	B
+
+Fig. 6.30  Hip joint. A. Articular surfaces. Anterior view. B. Movement of the neck of the femur during medial and lateral rotation. Superior view.
+
+
+
+Cut synovial membrane
+
+
+
+Acetabular labrum
+
+Acetabular fossa
+Lunate surface
+
+
+
+Synovial sleeve around ligament
+
+
+Obturator artery
+
+Pubic tubercle
+
+
+
+
+
+
+
+Acetabular foramen
+
+
+Transverse
+acetabular ligament	Obturator foramen
+
+Pubis
+
+Acetabular branch of obturator artery
+
+Artery of ligament of head
+
+Ligament of head of femur
+
+Obturator membrane
+
+
+A	B	Ischial tuberosity
+
+
+Fig. 6.31  Hip joint. A. Transverse acetabular ligament. B. Ligament of the head of the femur. The head of the femur has been laterally rotated
+out of the acetabulum to show the ligament.	551
+Lower Limb
+
+
+
+The ligament of the head of the femur is a flat band of delicate connective tissue that attaches at one end to the fovea on the head of the femur and at the other end to the acetabular  fossa,  transverse  acetabular  ligament,  and margins of the acetabular notch (Fig. 6.31B). It carries a small branch of the obturator artery, which contributes to the blood supply of the head of the femur.
+The synovial membrane attaches to the margins of the articular surfaces of the femur and acetabulum, forms a tubular covering around the ligament of the head of the femur, and lines the fibrous membrane of the joint (Figs. 6.31B and 6.32). From its attachment to the margin of the head of the femur, the synovial membrane covers the neck of the femur before reflecting onto the fibrous membrane (Fig. 6.32).
+The fibrous membrane that encloses the hip joint is strong and generally thick. Medially, it is attached to the margin of the acetabulum, the transverse acetabular liga-ment, and the adjacent margin of the obturator foramen (Fig. 6.33A). Laterally, it is attached to the intertrochan-teric line on the anterior aspect of the femur and to the neck of the femur just proximal to the intertrochanteric crest on the posterior surface.
+
+
+
+
+
+
+
+
+
+
+Synovial membrane
+
+Line of attachment around head
+of femur
+
+
+
+
+
+Membrane reflects back to attach to margin of acetabulum
+
+Fig. 6.32  Synovial membrane of the hip joint.
+
+
+
+
+
+
+
+
+
+
+Anterior inferior iliac spine
+
+
+
+
+
+
+Iliopubic eminence
+
+
+Iliofemoral ligament
+
+
+
+
+
+
+
+
+Intertrochanteric line	Pubofemoral ligament	Ischiofemoral ligament
+
+
+A	B	C
+
+Fig. 6.33  Fibrous membrane and ligaments of the hip joint. A. Fibrous membrane of the joint capsule. Anterior view. B. Iliofemoral and 552	pubofemoral ligaments. Anterior view. C. Ischiofemoral ligament. Posterior view.
+Regional Anatomy  •  Hip Joint	6
+
+
+Ligaments
+Three  ligaments  reinforce  the  external  surface  of  the fibrous membrane and stabilize the joint: the iliofemoral, pubofemoral, and ischiofemoral ligaments.
+
+
+■     The ischiofemoral ligament reinforces the posterior aspect  of  the  fibrous  membrane  (Fig.  6.33C).  It  is attached medially to the ischium, just posteroinferior to the acetabulum, and laterally to the greater trochanter deep to the iliofemoral ligament.
+
+
+
+■     The iliofemoral ligament is anterior to the hip joint and is triangular shaped (Fig. 6.33B). Its apex is attached to the ilium between the anterior inferior iliac spine and the margin of the acetabulum and its base is attached along the intertrochanteric line of the femur. Parts of the ligament attached above and below the intertro-chanteric line are thicker than the part attached to the central part of  the line. This results in the ligament having a Y appearance.
+■     The pubofemoral ligament is anteroinferior to the hip joint (Fig. 6.33B). It is also triangular in shape, with its base attached medially to the iliopubic eminence, adja-cent bone, and obturator membrane. Laterally, it blends with the fibrous membrane and with the deep surface of the iliofemoral ligament.
+
+
+The fibers of all three ligaments are oriented in a spiral fashion around the hip joint so that they become taut when the joint is extended. This stabilizes the joint and reduces the  amount  of  muscle  energy  required  to  maintain  a standing position.
+Vascular  supply  to  the  hip  joint  is  predominantly through  branches  of  the  obturator  artery,  medial  and lateral circumflex femoral arteries, superior and inferior gluteal arteries, and the first perforating branch of the deep artery of the thigh. The articular branches of these vessels form a network around the joint (Fig. 6.34).
+The hip joint is innervated by articular branches from the femoral, obturator, and superior gluteal nerves, and the nerve to the quadratus femoris.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Common iliac artery
+
+External iliac artery Internal iliac artery Superior gluteal artery
+
+Inferior gluteal artery
+
+
+
+Lateral circumflex femoral artery
+
+Medial circumflex femoral artery
+
+
+
+Deep artery of thigh
+
+
+1st perforating artery
+
+
+
+
+Fig. 6.34  Blood supply of the hip joint.
+
+
+Obturator artery
+
+Femoral artery
+
+
+
+
+553
+Lower Limb
+
+
+
+
+Gateways to the lower limb
+There are four major routes by which structures pass from the abdomen and pelvis into and out of  the lower limb. These are the obturator canal, the greater sciatic foramen, the lesser sciatic foramen, and the gap between the ingui-nal ligament and the anterosuperior margin of the pelvis (Fig. 6.35).
+
+Obturator canal
+The obturator canal is an almost vertically oriented pas-
+
+muscles (obturator internus and externus) attached to the inner and outer surfaces of the obturator membrane and surrounding bone.
+
+The  obturator  canal  connects  the  abdominopelvic region with the medial compartment of  the thigh. The obturator nerve and vessels pass through the canal.
+
+Greater sciatic foramen
+The greater sciatic foramen is formed on the posterolat-eral pelvic wall and is the major route for structures to pass
+
+sageway  at  the  anterosuperior  edge  of  the  obturator foramen (Fig. 6.35). It is bordered:
+
+between the pelvis and the gluteal region of the lower limb (Fig. 6.35). The margins of the foramen are formed by:
+
+
+
+■     above by a groove (obturator groove) on the inferior surface of the superior ramus of the pubic bone, and
+■     below by the upper margin of the obturator membrane, which  fills  most  of  the  obturator  foramen,  and  by
+
+■     the greater sciatic notch,
+■     parts of  the upper borders of  the sacrospinous and sacrotuberous ligaments, and
+■     the lateral border of the sacrum.
+
+
+
+Piriformis muscle	Abdominal cavity
+
+
+
+
+
+
+
+
+Greater sciatic foramen above piriformis muscle:
+• Superior gluteal nerve, artery, vein
+
+
+Lesser sciatic foramen:
+• Obturator internus muscle tendon
+• Pudendal nerve and internal pudendal vessels pass into perineum
+from gluteal region
+
+Greater sciatic foramen below piriformis muscle:
+• Sciatic nerve
+• Inferior gluteal nerve, artery, vein • Pudendal nerve
+• Internal pudendal artery and vein
+• Posterior femoral cutaneous nerve • Nerve to obturator internus and
+gemellus superior muscles
+• Nerve to quadratus femoris and gemellus inferior muscles
+
+
+
+
+Pelvic cavity
+
+
+
+
+
+
+
+Ilio-inguinal nerve
+Obturator canal: • obturator nerve
+• obturator vessels
+
+
+Gap between inguinal ligament and pelvic bone: • Psoas major, iliacus,
+pectineus muscles • Femoral artery
+• Femoral vein • Lymphatics
+• Femoral branch of genitofemoral nerve
+• Lateral cutaneous nerve of thigh
+• Femoral nerve
+
+
+
+Sacrotuberous ligament
+
+Sacrospinous ligament
+
+
+554	Fig. 6.35  Gateways to the lower limb.
+Regional Anatomy  •  Nerves	6
+
+
+
+The piriformis muscle passes out of the pelvis into the gluteal region through the greater sciatic foramen and separates the foramen into two parts, a part above the muscle and a part below:
+
+lower limb also pass through it, as does the femoral nerve, to enter the femoral triangle of the thigh.
+
+
+Nerves
+
+
+
+■     The superior gluteal nerve and vessels pass through the greater sciatic foramen above the piriformis.
+■     The sciatic nerve, inferior gluteal nerve and vessels, pudendal nerve and internal pudendal vessels, posterior cutaneous nerve of  the thigh, nerve to the obturator internus and gemellus superior, and nerve to the qua-dratus femoris and gemellus inferior pass through the greater sciatic foramen below the muscle.
+
+
+Nerves that enter the lower limb from the abdomen and pelvis are terminal branches of the lumbosacral plexus on the posterior wall of the abdomen and the posterolateral walls of the pelvis (Fig. 6.36 and Table 6.1).
+The lumbar plexus is formed by the anterior rami of spinal nerves L1 to L3 and part of L4 (see Chapter 4, pp. 398–401). The rest of the anterior ramus of L4 and the anterior ramus of L5 combine to form the lumbosacral trunk, which enters the pelvic cavity and joins with the
+
+
+
+
+Lesser sciatic foramen
+The lesser  sciatic  foramen is inferior to the greater sciatic  foramen  on  the  posterolateral  pelvic  wall  (Fig. 6.35). It is also inferior to the lateral attachment of the pelvic floor (levator ani and coccygeus muscles) to the pelvic wall and therefore connects the gluteal region with the perineum:
+
+anterior rami of S1 to S3 and part of S4 to form the sacral plexus (see Chapter 5, pp. 480–486).
+Major nerves that originate from the lumbosacral plexus and leave the abdomen and pelvis to enter the lower limb include the femoral nerve, obturator nerve, sciatic nerve, superior gluteal nerve, and inferior gluteal nerve. Other nerves that also originate from the plexus and enter the lower limb to supply skin or muscle include the lateral
+
+
+
+
+■     The tendon of the obturator internus passes from the lateral pelvic wall through the lesser sciatic foramen into the gluteal region to insert on the femur.
+■     The  pudendal  nerve  and  internal  pudendal  vessels, which first exit the pelvis by passing through the greater sciatic foramen below the piriformis muscle, enter the perineum below the pelvic floor by passing around the ischial spine and sacrospinous ligament and medially through the lesser sciatic foramen.
+
+cutaneous  nerve  of  the  thigh,  nerve  to  the  obturator internus, nerve to the quadratus femoris, posterior cutane-ous nerve of the thigh, perforating cutaneous nerve, and branches of the ilio-inguinal and genitofemoral nerves.
+
+Femoral nerve
+The femoral nerve carries contributions from the anterior rami of  L2 to L4 and leaves the abdomen by passing through the gap between the inguinal ligament and supe-rior margin of the pelvis to enter the femoral triangle on the anteromedial aspect of the thigh (Fig. 6.35 and Table
+
+
+
+Gap between the inguinal ligament and pelvic bone
+
+6.1). In the femoral triangle it is lateral to the femoral artery. The femoral nerve:
+
+
+
+The large crescent-shaped gap between the inguinal liga-ment above and the anterosuperior margin of the pelvic bone below is the major route of communication between the abdomen and the anteromedial aspect of the thigh (Fig. 6.35). The psoas major, iliacus, and pectineus muscles pass through this gap to insert onto the femur. The major blood vessels (femoral artery and vein) and lymphatics of  the
+
+■     innervates all muscles in the anterior compartment of the thigh,
+■     in the abdomen, gives rise to branches that innervate the iliacus and pectineus muscles, and
+■     innervates skin over the anterior aspect of the thigh, the anteromedial side of the knee, the medial side of the leg, and the medial side of the foot.
+
+
+
+
+
+
+
+
+
+
+555
+Lower Limb
+
+
+
+
+L1 anterior ramus
+
+L2 anterior ramus
+
+L3 anterior ramus
+
+
+
+
+
+Lumbosacral trunk
+
+Ilio-inguinal nerve	Superior gluteal nerve
+
+
+
+Lateral cutaneous nerve of thigh
+
+Sacrotuberous ligament
+
+Femoral branch of genitofemoral nerve
+
+S1	Inferior gluteal nerve S2
+Inguinal ligament
+
+Nerves to quadratus femoris and obturator internus
+
+
+Sacrospinous ligament
+
+
+
+
+Femoral nerve	Obturator nerve	Sciatic nerve Perforating cutaneous nerve
+
+Posterior cutaneous nerve of thigh
+
+
+
+
+Fig. 6.36  Branches of the lumbosacral plexus.
+
+
+
+Table 6.1    Branches of the lumbosacral plexus associated with the lower limb
+
+
+Branch
+Ilio-inguinal
+
+Genitofemoral
+
+
+
+
+
+Femoral
+
+
+
+Obturator
+
+
+556
+
+Spinal segments L1
+
+L1, L2
+
+
+
+
+
+L2 to L4
+
+
+
+L2 to L4
+
+Function: motor
+No motor function in lower limb, but innervates muscles of the abdominal wall
+No motor function in lower limb, but genital branch innervates cremaster muscle in the wall of the spermatic cord in men
+
+
+
+All muscles in the anterior compartment of thigh; in the abdomen, also gives rise to branches that supply iliacus and pectineus
+
+All muscles in the medial compartment of thigh (except pectineus and the part of adductor magnus attached to the ischium); also innervates obturator externus
+
+Function: sensory (cutaneous)
+Skin over anteromedial part of upper thigh and adjacent skin of perineum
+Femoral branch innervates skin on anterior central part of upper thigh; the genital branch innervates skin in anterior part of perineum (anterior scrotum in men, and mons pubis and anterior labia majora in women)
+Skin over the anterior thigh, anteromedial knee, medial side of the leg, and the medial side of the foot
+Skin over upper medial aspect of thigh
+Regional Anatomy  •  Nerves	6
+
+
+Table 6.1    Branches of the lumbosacral plexus associated with the lower limb—cont’d
+
+
+Branch Sciatic
+
+
+Superior gluteal
+
+
+Inferior gluteal
+
+Lateral cutaneous nerve of thigh
+Posterior cutaneous nerve of thigh
+
+
+Nerve to quadratus femoris
+
+Nerve to obturator internus
+
+Perforating cutaneous nerve
+
+Spinal segments L4 to S3
+
+
+L4 to S1
+
+
+L5 to S2
+
+L2, L3
+
+S1 to S3
+
+
+
+L4 to S1
+
+L5 to S2
+
+S2, S3
+
+Function: motor
+All muscles in the posterior compartment of thigh and the part of adductor magnus attached to the ischium; all muscles in the leg and foot
+Muscles of the gluteal region (gluteus medius, gluteus minimus, tensor fasciae latae)
+Muscle of the gluteal region (gluteus maximus)
+
+
+
+
+
+
+Muscles of gluteal region (quadratus femoris and gemellus inferior)
+Muscles of gluteal region (obturator internus and gemellus superior)
+
+Function: sensory (cutaneous)
+Skin over lateral side of leg and foot, and over the sole and dorsal surface of foot
+
+
+
+
+
+
+Parietal peritoneum in iliac fossa; skin over anterolateral thigh
+Skin over gluteal fold and upper medial aspect of thigh and adjacent perineum, posterior aspect of thigh and upper posterior leg
+
+
+
+
+Skin over medial aspect of gluteal fold
+
+
+
+
+
+
+
+Obturator nerve
+The obturator nerve, like the femoral nerve, originates from L2 to L4. It descends along the posterior abdominal wall, passes through the pelvic cavity and enters the thigh
+
+
+Posterior divisions of L4 to S2 are carried in the common fibular part of the nerve and the anterior divisions of L4 to S3 are carried in the tibial part.
+The sciatic nerve innervates:
+
+by passing through the obturator canal (Fig. 6.36 and Table 6.1). The obturator nerve innervates:
+
+
+■     all muscles in the posterior compartment of the thigh, ■     the part of the adductor magnus originating from the
+
+
+
+■     all muscles in the medial compartment of  the thigh, except the part of  the adductor magnus muscle that originates from the ischium and the pectineus muscle, which are innervated by the sciatic and the femoral
+
+ischium,
+■     all muscles in the leg and foot, and
+■     skin on the lateral side of the leg and the lateral side and sole of the foot.
+
+
+
+nerves, respectively;
+■     the obturator externus muscle; and
+■     skin on the medial side of the upper thigh.
+
+
+Gluteal nerves
+The gluteal nerves are major motor nerves of the gluteal
+
+
+
+Sciatic nerve
+
+The sciatic nerve is the largest nerve of  the body and carries contributions from L4 to S3. It leaves the pelvis through the greater sciatic foramen inferior to the pirifor-
+
+region.
+The superior gluteal nerve (Fig. 6.36 and Table 6.1) carries contributions from the anterior rami of L4 to S1, leaves the pelvis through the greater sciatic foramen above the piriformis muscle, and innervates:
+
+
+
+mis muscle, enters and passes through the gluteal region (Fig. 6.36 and Table 6.1), and then enters the posterior compartment of  the thigh where it divides into its two major branches:
+
+
+■     the gluteus medius and minimus muscles, and ■     the tensor fasciae latae muscle.
+
+The inferior gluteal nerve (Fig. 6.36 and Table 6.1)
+
+
+
+■     the common fibular nerve, and ■     the tibial nerve.
+
+is  formed  by  contributions  from  L5  to  S2,  leaves  the
+pelvis through the greater sciatic foramen inferior to the	557
+Lower Limb
+
+
+
+piriformis muscle, and enters the gluteal region to supply the gluteus maximus.
+
+■     The nerve to the quadratus femoris supplies the gemel-lus inferior and quadratus femoris muscles.
+
+
+
+Ilio-inguinal and genitofemoral nerves
+Terminal sensory branches of the ilio-inguinal nerve (L1) and the genitofemoral nerve (L1, L2) descend into the upper thigh from the lumbar plexus.
+The ilio-inguinal nerve originates from the superior part of the lumbar plexus, descends around the abdominal wall in the plane between the transversus abdominis and
+
+Posterior cutaneous nerve of thigh
+The posterior cutaneous nerve of the thigh is formed by contributions from S1 to S3 and leaves the pelvic cavity through the greater sciatic foramen inferior to the pirifor-mis muscle (Fig. 6.36 and Table 6.1). It passes vertically through the gluteal region deep to the gluteus maximus and enters the posterior thigh and innervates:
+
+
+
+internal oblique muscles, and then passes through the inguinal canal to leave the abdominal wall through the superficial inguinal ring (Fig. 6.36 and Table 6.1). Its ter-minal branches innervate skin on the medial side of the upper thigh and adjacent parts of the perineum.
+
+
+■     a longitudinal band of skin over the posterior aspect of the thigh that continues into the upper leg, and
+■     skin over the gluteal fold, over the upper medial part of the thigh and in the adjacent regions of the perineum.
+
+
+
+The  genitofemoral   nerve  passes  anteroinferiorly through the psoas major muscle on the posterior abdomi-nal wall and descends on the anterior surface of the psoas major (Fig. 6.36 and Table 6.1). Its genital branch inner-vates anterior aspects of the perineum. Its femoral branch passes into the thigh by crossing under the inguinal liga-ment where it is lateral to the femoral artery. It passes superficially to innervate skin over the upper central part of the anterior thigh.
+
+Lateral cutaneous nerve of thigh
+The lateral cutaneous nerve of  the thigh originates from L2 and L3. It leaves the abdomen either by passing through the gap between the inguinal ligament and the pelvic bone just medial to the anterior superior iliac spine or by passing directly through the inguinal ligament (Fig. 6.36 and Table 6.1). It supplies skin on the lateral side of the thigh.
+
+Nerve to quadratus femoris and nerve to obturator internus
+The nerve to the quadratus femoris (L4 to S1) and the nerve to the obturator internus (L5 to S2) are small motor nerves that originate from the sacral plexus. Both nerves pass through the greater sciatic foramen inferior to the piriformis muscle and enter the gluteal region (Fig. 6.36 and Table 6.1):
+
+
+Perforating cutaneous nerve
+The perforating cutaneous nerve is a small sensory nerve formed by contributions from S2 and S3. It leaves the pelvic cavity by penetrating directly through the sacrotu-berous  ligament  (Fig.  6.36  and Table  6.1)  and  passes inferiorly around the lower border of the gluteus maximus where it overlaps with the posterior cutaneous nerve of the thigh in innervating skin over the medial aspect of  the gluteal fold.
+
+Arteries Femoral artery
+The major artery supplying the lower limb is the femoral artery (Fig. 6.37), which is the continuation of the exter-nal iliac artery in the abdomen. The external iliac artery becomes the femoral artery as the vessel passes under the inguinal  ligament  to  enter  the  femoral  triangle  in  the anterior aspect of the thigh. Branches supply most of the thigh and all of the leg and foot.
+
+Superior and inferior gluteal arteries and the obturator artery
+Other vessels supplying parts of the lower limb include the superior and inferior gluteal arteries and the obturator artery (Fig. 6.37).
+The superior and inferior gluteal arteries originate in the pelvic cavity as branches of the internal iliac artery
+
+
+
+■     The nerve to the obturator internus supplies the gemel-lus superior muscle in the gluteal region and then loops around  the  ischial  spine  and  enters  the  perineum through the lesser sciatic foramen to penetrate the peri-neal surface of the obturator internus muscle.
+
+(see Chapter 5, pp. 489–492) and supply the gluteal region. The superior gluteal artery leaves the pelvis through the greater sciatic foramen above the piriformis muscle, and the inferior gluteal artery leaves through the same foramen but below the piriformis muscle.
+
+
+
+
+558
+Regional Anatomy  •  Arteries	6
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+LI
+Aorta
+
+LII
+
+LIII	Common iliac artery
+
+Internal iliac artery
+
+
+External iliac artery
+
+
+
+
+
+Superior gluteal artery
+
+Piriformis muscle
+
+Inferior gluteal artery
+
+Sacrotuberous ligament
+
+
+Superior gluteal artery Obturator artery
+
+Inferior gluteal artery
+Femoral vein
+
+
+Obturator foramen and membrane
+Femoral artery
+
+
+Obturator canal
+
+Sacrospinous ligament
+
+
+
+
+
+Fig. 6.37  Arteries of the lower limb.
+
+
+
+
+
+
+
+
+
+
+559
+Lower Limb
+
+
+
+The obturator artery is also a branch of the internal iliac artery in the pelvic cavity (see Chapter 5, pp. 490–491) and passes through the obturator canal to enter and supply the medial compartment of the thigh.
+Branches  of   the  femoral,  inferior  gluteal,  superior gluteal, and obturator arteries, together with branches from  the  internal  pudendal  artery  of   the  perineum, interconnect  to  form  an  anastomotic  network  in  the upper thigh and gluteal region. The presence of  these anastomotic channels may provide collateral circulation when one of the vessels is interrupted.
+
+
+Inferior vena cava
+
+Common iliac vein
+
+Internal iliac vein
+
+External iliac vein
+
+Inguinal ligament
+
+Inferior and superior gluteal veins
+
+Obturator vein
+
+
+
+
+Veins
+Veins draining the lower limb form superficial and deep groups.
+The deep veins generally follow the arteries (femoral, superior gluteal, inferior gluteal, and obturator). The major deep vein draining the limb is the femoral vein (Fig. 6.38). It becomes the external iliac vein when it passes under the inguinal ligament to enter the abdomen.
+The superficial veins are in the subcutaneous connec-tive tissue and are interconnected with and ultimately drain into the deep veins. The superficial veins form two major channels—the great saphenous vein and the small saphenous vein. Both veins originate from a dorsal venous arch in the foot:
+
+Femoral vein
+
+
+
+
+
+
+
+
+
+
+Popliteal vein
+
+
+
+Anterior and posterior tibial veins
+
+
+
+■     The great saphenous vein originates from the medial side of the dorsal venous arch and then ascends up the medial side of the leg, knee, and thigh to connect with the femoral vein just inferior to the inguinal ligament.
+■     The small saphenous vein originates from the lateral side of the dorsal venous arch, ascends up the posterior surface of the leg, and then penetrates deep fascia to join the popliteal vein posterior to the knee; proximal to the knee, the popliteal vein becomes the femoral vein.
+
+
+Small saphenous vein
+
+Great saphenous vein
+
+
+
+
+Superficial veins
+
+
+
+
+
+
+
+Fig. 6.38  Veins of the lower limb.
+
+
+
+
+
+
+
+
+
+560
+Regional Anatomy  •  Veins	6
+
+
+
+In the clinic
+
+Varicose veins
+The normal flow of blood in the lower limbs is from the skin and subcutaneous tissues to the superficial veins, which drain via perforating veins to the deep veins, which
+in turn drain into the iliac veins and inferior vena cava.
+The normal flow of blood in the venous system depends upon the presence of competent valves, which prevent reflux. Venous return is supplemented with contraction of the muscles in the lower limb, which pump the blood toward the heart. When venous valves become incompetent they tend to place extra pressure on more distal valves, which may also become incompetent. This condition produces dilated tortuous superficial veins (varicose veins) in the distribution of the great (long) and small (short) saphenous venous systems.
+Varicose veins occur more commonly in women than in men, and symptoms are often aggravated by pregnancy. Some individuals have a genetic predisposition to developing varicose veins. Valves may also be destroyed when a deep vein thrombosis occurs if the clot incorporates
+
+
+
+
+
+
+
+In the clinic
+
+Deep vein thrombosis
+Thrombosis may occur in the deep veins of the lower limb and within the pelvic veins. Its etiology was eloquently described by Virchow, who described the classic triad (venous stasis, injury to the vessel wall, and hypercoagulable states) that precipitates thrombosis.
+In some patients a deep vein thrombosis (DVT) in the calf veins may propagate into the femoral veins. This clot may break off and pass through the heart to enter the pulmonary circulation, resulting in occlusion of the pulmonary artery, cardiopulmonary arrest, and death.
+A significant number of patients undergoing surgery are likely to develop a DVT, so most surgical patients are given
+
+
+
+the valve into its interstices; during the process of healing and recanalization the valve is destroyed, rendering it incompetent.
+Typical sites for valvular incompetence include the junction between the great (long) saphenous vein and the femoral vein, perforating veins in the midthigh, and the junction between the small (short) saphenous vein and the popliteal vein.
+Varicose veins may be unsightly, and soft tissue changes may occur with chronic venous incompetence. As the venous pressure rises, increased venular and capillary pressure damages the cells, and blood and blood products extrude into the soft tissue. This may produce a brown pigmentation in the skin, and venous eczema may develop. Furthermore, if the pressure remains high the skin may break down and ulcerate, and many weeks of hospitalization may be needed for this to heal.
+Treatments for varicose veins include tying off the valve, “stripping” (removing) the great (long) and small (short) saphenous systems, and in some cases valvular reconstruction.
+
+
+
+
+
+
+
+
+
+specific prophylactic treatment to prevent thrombosis. A typical DVT prophylactic regimen includes anticoagulant injections and graduated stockings (to prevent deep venous stasis and facilitate emptying of the deep veins).
+Although physicians aim to prevent the formation of DVT, it is not always possible to detect it because there may be no clinical signs. Calf muscle tenderness, postoperative pyrexia, and limb swelling can be helpful clues. The diagnosis is predominantly made by duplex Doppler sonography or rarely by ascending venography.
+If DVT is confirmed, intravenous and oral anticoagulation are started to prevent extension of the thrombus.
+
+
+
+
+
+
+
+
+
+
+
+
+561
+Lower Limb
+
+
+
+
+Lymphatics
+Most lymphatic vessels in the lower limb drain into super-ficial and deep inguinal nodes located in the fascia just inferior to the inguinal ligament (Fig. 6.39).
+
+Superficial inguinal nodes
+The superficial inguinal nodes, approximately ten in number, are in the superficial fascia and parallel the course of the inguinal ligament in the upper thigh. Medially, they extend  inferiorly  along  the  terminal  part  of  the  great saphenous vein.
+
+Superficial inguinal nodes receive lymph from the gluteal region, lower abdominal wall, perineum, and superficial regions of  the lower limb. They drain, via vessels that accompany the femoral vessels, into external iliac nodes associated with the external iliac artery in the abdomen.
+
+Deep inguinal nodes
+The deep inguinal nodes, up to three in number, are medial to the femoral vein (Fig. 6.39).
+The deep inguinal nodes receive lymph from deep lym-phatics associated with the femoral vessels and from the glans penis (or clitoris) in the perineum. They interconnect
+
+
+
+
+
+
+
+
+
+
+External iliac nodes
+
+
+Superficial inguinal nodes	Inguinal ligament
+Deep inguinal nodes
+
+
+
+
+
+
+
+
+
+
+Great saphenous vein
+
+
+
+
+
+
+
+
+
+
+Popliteal nodes (deep) (behind knee)
+
+
+
+
+
+562	Fig. 6.39  Lymphatic drainage of the lower limb.
+Regional Anatomy  •  Deep Fascia and the Saphenous Opening	6
+
+
+
+with the superficial inguinal nodes and drain into the external iliac nodes via vessels that pass along the medial side of the femoral vein as it passes under the inguinal liga-ment. The space through which the lymphatic vessels pass under the inguinal ligament is the femoral canal.
+
+Popliteal nodes
+In addition to the inguinal nodes, there is a small collection of deep nodes posterior to the knee close to the popliteal vessels   (Fig.   6.39).   These   popliteal   nodes   receive lymph from superficial vessels, which accompany the small saphenous vein, and from deep areas of the leg and foot. They ultimately drain into the deep and superficial inguinal nodes.
+
+
+Deep fascia and the saphenous opening Fascia lata
+The outer layer of deep fascia in the lower limb forms a thick “stocking-like” membrane, which covers the limb and lies beneath the superficial fascia (Fig. 6.40A). This deep fascia is particularly thick in the thigh and gluteal region and is termed the fascia lata.
+The  fascia  lata  is  anchored  superiorly  to  bone  and soft tissues along a line of  attachment that defines the upper margin of the lower limb. Beginning anteriorly and circling laterally around the limb, this line of attachment
+
+
+Anterior superior iliac spine
+
+
+
+Inguinal ligament
+
+
+
+Pubic tubercle
+
+Saphenous opening
+
+Anterior superior iliac spine
+Inguinal ligament
+Pubic tubercle Fascia lata
+Tensor fascia lata
+
+Gluteus maximus
+
+Fascia lata
+
+Deep fascia of leg
+
+Iliotibial tract
+
+
+
+
+
+
+
+
+Tuberculum of iliac crest
+
+
+
+includes the inguinal ligament, iliac crest, sacrum, coccyx, sacrotuberous  ligament,  inferior  ramus  of   the  pubic bone, body of the pubic bone, and superior ramus of the pubic bone.
+Inferiorly, the fascia lata is continuous with the deep fascia of the leg.
+
+Iliotibial tract
+The fascia lata is thickened laterally into a longitudinal
+
+
+A	B
+
+Fig. 6.40  Fascia lata. A. Right limb. Anterior view. B. Lateral view.
+
+
+
+band  (the  iliotibial  tract),  which  descends  along  the lateral margin of the limb from the tuberculum of the iliac crest to a bony attachment just below the knee (Fig. 6.40B). The superior aspect of  the fascia lata in the gluteal region splits anteriorly to enclose the tensor fasciae latae
+
+
+■     Most of  the gluteus maximus muscle inserts into the posterior aspect of the iliotibial tract.
+
+The tensor fasciae latae and gluteus maximus muscles,
+
+
+
+muscle and posteriorly to enclose the gluteus maximus muscle:
+
+working through their attachments to the iliotibial tract, hold the leg in extension once other muscles have extended the leg at the knee joint. The iliotibial tract and its two
+
+
+
+■     The tensor fasciae latae muscle is partially enclosed by and inserts into the superior and anterior aspects of the iliotibial tract.
+
+associated muscles also stabilize the hip joint by preventing lateral displacement of the proximal end of the femur away from the acetabulum.
+
+
+
+
+
+563
+Lower Limb
+
+
+
+
+Saphenous opening
+The fascia lata has one prominent aperture on the anterior aspect of the thigh just inferior to the medial end of the inguinal  ligament  (the  saphenous  opening),  which allows the great saphenous vein to pass from superficial fascia through the deep fascia to connect with the femoral vein (Fig. 6.41).
+The margin of the saphenous opening is formed by the free medial edge of the fascia lata as it descends from the inguinal ligament and spirals around the lateral side of the great saphenous vein and medially under the femoral vein to attach to the pectineal line (pecten pubis) of the pelvic bone.
+
+■     The lateral margin is the medial margin of the sartorius muscle in the anterior compartment of the thigh.
+■     The floor of the triangle is formed medially by the pec-tineus  and  adductor  longus  muscles  in  the  medial compartment of the thigh and laterally by the iliopsoas muscle descending from the abdomen.
+■     The apex of the femoral triangle points inferiorly and is continuous  with  a  fascial  canal  (adductor  canal), which descends medially down the thigh and posteriorly through an aperture in the lower end of  one of  the largest of the adductor muscles in the thigh (the adduc-tor magnus muscle) to open into the popliteal fossa behind the knee.
+
+
+
+
+Femoral triangle
+The femoral triangle is a wedge-shaped depression formed by muscles in the upper thigh at the junction between the anterior abdominal wall and the lower limb (Fig. 6.42):
+
+The femoral nerve, artery, and vein and lymphatics pass  between  the  abdomen  and  lower  limb  under  the
+
+
+■     The base of the triangle is the inguinal ligament.
+■     The medial border is the medial margin of the adductor longus muscle in the medial compartment of the thigh.
+
+
+Inguinal ligament
+
+
+Pelvic inlet
+
+External iliac vein
+
+
+
+Anterior superior iliac spine
+
+Pubic symphysis
+
+Femoral triangle Pectineus muscle
+Adductor longus muscle Gracilis muscle
+Adductor magnus muscle
+
+
+
+
+Inguinal ligament
+
+
+
+Pectineal line
+
+Saphenous ring
+Femoral vein
+
+Sartorius muscle
+
+
+
+Adductor hiatus
+
+
+
+Femoral triangle
+
+
+Fascia lata
+
+
+
+Adductor canal
+Great saphenous vein	Pubic tubercle Pubic bone
+Pubic symphysis
+
+564	Fig. 6.41  Saphenous ring. Anterior view.	Fig. 6.42  Boundaries of the femoral triangle.
+Regional Anatomy  •  Femoral Triangle	6
+
+
+
+inguinal ligament and in the femoral triangle (Fig. 6.43). The femoral artery and vein pass inferiorly through the adductor canal and become the popliteal vessels behind the knee where they meet and are distributed with branches of the sciatic nerve, which descends through the posterior thigh from the gluteal region.
+From lateral to medial, major structures in the femoral triangle are the femoral nerve, the femoral artery, the femoral vein, and lymphatic vessels. The femoral artery can be palpated in the femoral triangle just inferior to the inguinal ligament and midway between the anterior supe-rior iliac spine and the pubic symphysis.
+
+Femoral sheath
+In the femoral triangle, the femoral artery and vein and the associated lymphatic vessels are surrounded by a funnel-shaped sleeve of fascia (the femoral sheath). The sheath is continuous superiorly with the transversalis fascia and iliac fascia of the abdomen and merges inferiorly with con-nective tissue associated with the vessels. Each of the three structures surrounded by the sheath is contained within a separate fascial compartment within the sheath. The most medial  compartment  (the  femoral  canal)  contains  the lymphatic vessels and is conical in shape. The opening of this canal superiorly is potentially a weak point in the lower abdomen and is the site for femoral hernias. The femoral nerve is lateral to and not contained within the femoral sheath.
+
+In the clinic
+
+
+Aorta Inferior vena cava
+
+Psoas major
+
+
+Inguinal ligament
+
+Femoral nerve Femoral sheath
+Lymphatics in femoral canal
+
+Femoral artery
+
+Femoral vein
+
+
+
+
+
+Adductor canal
+
+
+
+
+
+
+
+
+
+
+
+Popliteal artery behind knee
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Pubic symphysis
+
+
+
+Vascular access to the lower limb
+Deep and inferior to the inguinal ligament are the femoral artery and femoral vein. The femoral artery is palpable as it passes over the femoral head and may be easily demonstrated using ultrasound. If arterial or venous access is needed rapidly, a physician can use the femoral approach to these vessels.
+Many radiological procedures involve catheterization of the femoral artery or the femoral vein to obtain access to the contralateral lower limb, the ipsilateral lower limb, the vessels of the thorax and abdomen, and the cerebral vessels.
+Cardiologists also use the femoral artery to place catheters in vessels around the arch of the aorta and into the coronary arteries to perform coronary angiography and angioplasty.
+Access to the femoral vein permits catheters to be maneuvered into the renal veins, the gonadal veins, the right atrium, and the right side of the heart, including the pulmonary artery and distal vessels of the pulmonary tree. Access to the superior vena cava and the great veins of the neck is also possible.
+
+
+Anterior iliac spine
+
+
+
+Inguinal ligament
+Pubic tubercle
+
+Femoral nerve	Pubic Femoral artery	symphysis
+Lymphatics Femoral vein
+
+Sartorius	Adductor longus
+
+
+
+
+
+Fig. 6.43  Contents of the femoral triangle.
+
+
+
+
+565
+Lower Limb
+
+
+
+GLUTEAL REGION
+
+The gluteal region lies posterolateral to the bony pelvis and proximal end of  the femur (Fig. 6.44). Muscles in the region  mainly  abduct,  extend,  and  laterally  rotate  the femur relative to the pelvic bone.
+The gluteal region communicates anteromedially with the pelvic cavity and perineum through the greater sciatic
+
+foramen and lesser sciatic foramen, respectively. Inferiorly, it is continuous with the posterior thigh.
+The sciatic nerve enters the lower limb from the pelvic cavity by passing through the greater sciatic foramen and descending through the gluteal region into the posterior thigh and then into the leg and foot.
+The pudendal nerve and internal pudendal vessels pass between the pelvic cavity and perineum by passing first through the greater sciatic foramen to enter the gluteal
+
+
+
+Greater sciatic foramen
+
+Sacrotuberous ligament
+
+region and then immediately passing through the lesser sciatic foramen to enter the perineum. The nerve to the obturator internus and gemellus superior follows a similar course. Other nerves and vessels that pass through the greater sciatic foramen from the pelvic cavity supply struc-tures in the gluteal region itself.
+
+
+
+Muscles
+Muscles of  the gluteal region (Table 6.2) are composed Sacrospinous ligament	mainly of two groups:
+
+■     a deep group of small muscles, which are mainly lateral rotators of the femur at the hip joint and include the piriformis,   obturator   internus,   gemellus   superior, gemellus inferior, and quadratus femoris;
+■     a  more  superficial  group  of  larger  muscles,  which
+
+
+
+
+Lesser sciatic foramen
+
+
+Quadrate tubercle
+
+
+Gluteal tuberosity
+
+mainly  abduct  and  extend  the  hip  and  include  the gluteus minimus, gluteus medius, and gluteus maximus; an additional muscle in this group, the tensor fasciae latae, stabilizes the knee in extension by acting on a specialized longitudinal band of deep fascia (the iliotibial tract) that passes down the lateral side of the thigh to attach to the proximal end of the tibia in the leg.
+
+
+
+
+
+Fig. 6.44  Gluteal region. Posterior view.
+
+Many of the important nerves in the gluteal region are in the plane between the superficial and deep groups of muscles.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+566
+Regional Anatomy  •  Gluteal Region	6
+
+
+Table 6.2    Muscles of the gluteal region (spinal segments in bold are the major segments innervating the muscle)
+
+
+Muscle Piriformis
+
+
+Obturator internus
+
+
+
+Gemellus superior
+
+
+
+
+
+Gemellus inferior
+
+
+
+
+
+Quadratus femoris
+
+
+Gluteus minimus
+
+
+
+
+
+Gluteus medius
+
+
+
+
+
+Gluteus maximus
+
+
+
+
+
+Tensor fasciae latae
+
+Origin
+Anterior surface of sacrum between anterior sacral foramina
+Anterolateral wall of true pelvis; deep surface of obturator membrane and surrounding bone
+External surface of ischial spine
+
+
+
+
+
+Upper aspect of ischial tuberosity
+
+
+
+
+Lateral aspect of the ischium just anterior to the ischial tuberosity
+External surface of ilium between inferior and anterior gluteal lines
+
+
+
+External surface of ilium between anterior and posterior gluteal lines
+
+
+
+Fascia covering gluteus medius, external surface of ilium behind posterior gluteal line, fascia of erector spinae, dorsal surface of lower sacrum, lateral margin of coccyx, external surface of sacrotuberous ligament
+Lateral aspect of crest of ilium between anterior superior iliac spine and tubercle of the crest
+
+Insertion
+Medial side of superior border of greater trochanter of femur
+
+Medial side of greater trochanter of femur
+
+
+Along length of superior surface of the obturator internus tendon and into the medial side of greater trochanter of femur with obturator internus tendon
+Along length of inferior surface of the obturator internus tendon and into the medial side of greater trochanter of femur with obturator internus tendon
+Quadrate tubercle on the intertrochanteric crest of the proximal femur
+Linear facet on the anterolateral aspect of the greater trochanter
+
+
+
+Elongate facet on the lateral surface of the greater trochanter
+
+
+
+Posterior aspect of iliotibial tract of fascia lata and gluteal tuberosity of proximal femur
+
+
+
+
+Iliotibial tract of fascia lata
+
+Innervation
+Branches from S1 and S2
+
+Nerve to obturator internus (L5, S1)
+
+
+Nerve to obturator internus (L5, S1)
+
+
+
+
+Nerve to quadratus femoris (L5, S1)
+
+
+
+
+Nerve to quadratus femoris (L5, S1)
+
+Superior gluteal nerve (L4, L5, S1)
+
+
+
+
+Superior gluteal nerve (L4, L5, S1)
+
+
+
+
+Inferior gluteal nerve (L5, S1, S2)
+
+
+
+
+
+Superior gluteal nerve (L4, L5, S1)
+
+Function
+Laterally rotates the extended femur at hip joint; abducts flexed femur at hip joint
+Laterally rotates the extended femur at hip joint; abducts flexed femur at hip joint
+
+Laterally rotates the extended femur at hip joint; abducts flexed femur at hip joint
+
+
+
+Laterally rotates the extended femur at hip joint; abducts flexed femur at hip joint
+
+
+
+Laterally rotates femur at hip joint
+
+Abducts femur at hip joint; holds pelvis secure over stance leg and prevents pelvic drop on the opposite swing side during walking; medially rotates thigh
+Abducts femur at hip joint; holds pelvis secure over stance leg and prevents pelvic drop on the opposite swing side during walking; medially rotates thigh
+Powerful extensor of flexed femur at hip joint; lateral stabilizer of hip joint and knee joint; laterally rotates and abducts thigh
+
+
+Stabilizes the knee in extension
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+567
+Lower Limb
+
+
+
+
+Deep group Piriformis
+The piriformis muscle is the most superior of  the deep group of muscles (Fig. 6.45) and is a muscle of the pelvic wall and of the gluteal region (see Chapter 5, p. 443). It originates from between the anterior sacral foramina on the anterolateral surface of the sacrum and passes laterally and inferiorly through the greater sciatic foramen.
+In the gluteal region, the piriformis passes posterior to
+
+Obturator internus
+The  obturator  internus  muscle,  like  the  piriformis muscle, is a muscle of the pelvic wall and of the gluteal region (Fig. 6.45). It is a flat fan-shaped muscle originating from the medial surface of the obturator membrane and adjacent bone of the obturator foramen (see Chapter 5, pp. 442–443). Because the pelvic floor attaches to a thickened band of fascia across the medial surface of the obturator internus, the obturator internus forms:
+
+
+
+the hip joint and attaches to a facet on the upper margin of the greater trochanter of the femur.
+The piriformis externally rotates and abducts the femur at the hip joint and is innervated in the pelvic cavity by the nerve to the piriformis, which originates as branches from S1 and S2 of the sacral plexus (see Chapter 5, p. 485).
+In addition to its action on the hip joint, the piriformis
+
+
+■     the anterolateral wall of  the pelvic cavity above the pelvic floor, and
+■     the lateral wall of the ischio-anal fossa in the perineum below the pelvic floor.
+
+The muscle fibers of the obturator internus converge to
+
+
+
+is an important landmark because it divides the greater sciatic foramen into two regions, one above and one below the piriformis. Vessels and nerves pass between the pelvis and gluteal region by passing through the greater sciatic foramen either above or below the piriformis.
+
+form  a  tendon,  which  bends  90°  around  the  ischium between the ischial spine and ischial tuberosity and passes through the lesser sciatic foramen to enter the gluteal region. The tendon then passes posteroinferiorly to the hip joint and attaches to the medial surface of  the superior
+
+
+
+
+
+Gluteus medius
+
+
+
+Gluteus minimus
+
+
+
+
+
+Greater sciatic foramen above piriformis
+Piriformis muscle
+
+Gemellus superior
+
+
+
+
+Contraction of gluteus minimus and medius
+on stance side prevents excessive pelvic tilt during swing phase
+on opposite side
+
+
+
+
+
+Obturator internus
+
+Greater sciatic foramen below piriformis
+A
+
+Gemellus inferior
+
+Quadratus femoris
+
+
+
+B
+
+
+568	Fig. 6.45  Deep muscles in the gluteal region. A. Posterior view. B. Function.
+Regional Anatomy  •  Gluteal Region	6
+
+
+
+margin of the greater trochanter of the femur just inferior to the attachment of the piriformis muscle.
+The obturator internus laterally rotates and abducts the femur at the hip joint and is innervated by the nerve to the obturator internus.
+
+Gemellus superior and inferior
+The gemellus superior and inferior (gemelli is Latin for “twins”) are a pair of triangular muscles associated with the upper and lower margins of  the obturator internus tendon (Fig. 6.45):
+
+The gluteus  minimus is a fan-shaped muscle that originates from the external surface of the expanded upper part of the ilium, between the inferior gluteal line and the anterior gluteal line. The muscle fibers converge inferiorly and laterally to form a tendon, which inserts into a broad linear  facet  on  the  anterolateral  aspect  of  the  greater trochanter.
+The gluteus medius overlies the gluteus minimus and is also fan shaped. It has a broad origin from the external surface of the ilium between the anterior gluteal line and posterior gluteal line and inserts on an elongate facet on
+
+
+
+
+■     The base of the gemellus superior originates from the gluteal surface of the ischial spine.
+■     The base of the gemellus inferior originates from the upper   gluteal   and   pelvic   surfaces   of   the   ischial tuberosity.
+
+the lateral surface of the greater trochanter.
+The gluteus medius and minimus muscles abduct the lower limb at the hip joint and reduce pelvic drop over the opposite swing limb during walking by securing the posi-tion of  the pelvis on the stance limb (Fig. 6.45B). Both muscles are innervated by the superior gluteal nerve.
+
+
+
+Fibers of the gemellus muscles attach along the length of the obturator internus tendon, and the apices of the two muscles insert with the tendon of the obturator internus on the greater trochanter of the femur.
+The gemellus superior is innervated by the nerve to the obturator internus, and the gemellus inferior is innervated by  the  nerve  to  the  quadratus  femoris.  The  gemellus muscles act with the obturator internus muscle to laterally rotate and abduct the femur at the hip joint.
+
+Quadratus femoris
+The quadratus femoris muscle is the most inferior of the deep group of muscles in the gluteal region (Fig. 6.45). It is a flat rectangular muscle below the obturator internus muscle and its associated gemellus muscles.
+The quadratus femoris is attached at one end to a linear roughening on the lateral aspect of the ischium just ante-rior to the ischial tuberosity and at the other end to the quadrate tubercle on the intertrochanteric crest of  the proximal femur.
+The quadratus femoris laterally rotates the femur at the hip joint and is innervated by the nerve to the quadratus femoris.
+
+Superficial group
+Gluteus minimus and medius
+
+
+
+In the clinic
+
+Trendelenburg’s sign
+Trendelenburg’s sign occurs in people with weak or paralyzed abductor muscles (gluteus medius and gluteus minimus) of the hip. The sign is demonstrated by asking the patient to stand on one limb. When the patient stands on the affected limb, the pelvis severely drops over the swing limb.
+Positive signs are typically found in patients with damage to the superior gluteal nerve. Damage to this nerve may occur with associated pelvic fractures, with space-occupying lesions within the pelvis extending into the greater sciatic foramen, and in some cases relating to hip surgery during which there has been disruption of and subsequent atrophy of the insertion of the gluteus medius and gluteus minimus tendons on the greater trochanter.
+In patients with a positive Trendelenburg’s sign, gait also is abnormal. Typically during the stance phase of the affected limb, the weakened abductor muscles allow the pelvis to tilt inferiorly over the swing limb. The patient compensates for the pelvic drop by lurching the trunk to the affected side to maintain the level of the pelvis throughout the gait cycle.
+
+The  gluteus  minimus  and  medius  muscles  are  two muscles of the more superficial group in the gluteal region (Fig. 6.45).
+
+
+
+
+569
+Lower Limb
+
+
+
+
+Gluteus maximus
+The gluteus maximus is the largest muscle in the gluteal region and overlies most of the other gluteal muscles (Fig. 6.46).
+The gluteus maximus is quadrangular in shape and has a broad origin extending from a roughened area of  the ilium behind the posterior gluteal line and along the dorsal surface of the lower sacrum and the lateral surface of the coccyx to the external surface of the sacrotuberous liga-ment. It is also attached to fascia overlying the gluteus medius muscle and, between the ilium and sacrum, to fascia covering the erector spinae muscle, and is often described as being enclosed within two layers of the fascia lata, which covers the thigh and gluteal region.
+Laterally, the upper and superficial lower parts of the gluteus maximus insert into the posterior aspect of a ten-dinous thickening of  the fascia lata (the iliotibial tract), which passes over the lateral surface of  the greater tro-chanter and descends down the thigh and into the upper leg. Deep distal parts of the muscle attach to the elongate gluteal tuberosity of the proximal femur.
+The gluteus maximus mainly extends the flexed thigh at the hip joint. Through its insertion into the iliotibial tract,
+
+
+
+
+
+Gluteus medius
+
+it also stabilizes the knee and hip joints. It is innervated by the inferior gluteal nerve.
+
+Tensor fasciae latae
+The tensor fasciae latae muscle is the most anterior of the superficial group of  muscles in the gluteal region and overlies the gluteus minimus and the anterior part of the gluteus medius (Fig. 6.47).
+The tensor fasciae latae originates from the outer margin of the iliac crest from the anterior superior iliac spine to approximately the tuberculum of the iliac crest. The muscle
+
+
+Tubercle of crest of ilium
+
+Gluteus medius
+
+
+
+Gluteus minimus
+
+Gluteus maximus
+
+Tensor fasciae latae
+
+
+
+
+
+
+
+Iliotibial tract
+
+
+
+
+
+Gluteus maximus
+
+Fascia lata
+
+
+
+
+Attachment of gluteus maximus to iliotibial tract
+
+
+
+
+Attachment of deep fibers to gluteal tuberosity
+
+Attachment to tibia
+
+Tibia
+
+
+Iliotibial tract	Deep fascia of leg
+
+
+570	Fig. 6.46  Gluteus maximus muscle. Posterior view.	Fig. 6.47  Tensor fasciae latae. Left gluteal region, lateral view.
+Regional Anatomy  •  Gluteal Region	6
+
+
+
+fibers descend to insert into the anterior aspect of  the iliotibial tract of deep fascia, which runs down the lateral side of the thigh and attaches to the upper tibia. Like the gluteus maximus muscle, the tensor fasciae latae is enclosed within a compartment of the fascia lata.
+The tensor fasciae latae stabilizes the knee in extension and, working with the gluteus maximus muscle on the iliotibial tract lateral to the greater trochanter, stabilizes the hip joint by holding the head of the femur in the ace-tabulum (Fig. 6.47). It is innervated by the superior gluteal nerve.
+
+Nerves
+Seven  nerves  enter  the  gluteal  region  from  the  pelvis through the greater sciatic foramen (Fig. 6.48): the supe-rior gluteal nerve, sciatic nerve, nerve to the quadratus femoris, nerve to the obturator internus, posterior cutane-ous nerve of the thigh, pudendal nerve, and inferior gluteal nerve.
+An additional nerve, the perforating cutaneous nerve, enters the gluteal region by passing directly through the sacrotuberous ligament.
+Some of these nerves, such as the sciatic and pudendal nerves, pass through the gluteal region en route to other
+
+areas. Nerves such as the superior and inferior gluteal nerves innervate structures in the gluteal region. Many of the nerves in the gluteal region are in the plane between the superficial and deep groups of muscles.
+
+Superior gluteal nerve
+Of  all the nerves that pass through the greater sciatic foramen, the superior gluteal nerve is the only one that passes above the piriformis muscle (Fig. 6.48). After enter-ing the gluteal region, the nerve loops up over the inferior margin of the gluteus minimus and travels anteriorly and laterally in the plane between the gluteus minimus and medius muscles.
+The superior gluteal nerve supplies branches to the gluteus minimus and medius muscles and terminates by innervating the tensor fasciae latae muscle.
+
+Sciatic nerve
+The sciatic nerve enters the gluteal region through the greater sciatic foramen inferior to the piriformis muscle (Fig. 6.48). It descends in the plane between the superficial and deep group of  gluteal region muscles, crossing the posterior surfaces of first the obturator internus and asso-ciated gemellus muscles and then the quadratus femoris
+
+
+
+
+
+
+
+
+Tensor fasciae latae muscle
+
+Pudendal nerve
+Superior gluteal nerve
+
+
+
+
+
+Nerve to obturator internus
+
+Nerve to quadratus femoris muscle (deep to gemelli, obturator internus, and quadratus femoris)
+
+Piriformis muscle
+
+
+Inferior gluteal nerve
+
+
+
+
+Perforating cutaneous nerve
+Gluteus maximus Posterior cutaneous nerve of thigh
+
+
+Sciatic nerve
+
+
+
+Fig. 6.48  Nerves of the gluteal region. Posterior view.
+
+
+Iliotibial tract
+
+
+571
+Lower Limb
+
+
+
+muscle. It lies just deep to the gluteus maximus at the midpoint between the ischial tuberosity and the greater trochanter. At the lower margin of the quadratus femoris muscle, the sciatic nerve enters the posterior thigh.
+The sciatic nerve is the largest nerve in the body and innervates all muscles in the posterior compartment of the thigh that flex the knee and all muscles that work the ankle and foot. It also innervates a large area of skin in the lower limb.
+
+Nerve to quadratus femoris
+The nerve to the quadratus femoris enters the gluteal region through the greater sciatic foramen inferior to the piriformis muscle and deep to the sciatic nerve (Fig. 6.48). Unlike other nerves in the gluteal region, the nerve to the quadratus femoris lies anterior to the plane of  the deep muscles.
+The nerve to the quadratus femoris descends along the ischium  deep  to  the  tendon  of  the  obturator  internus muscle and associated gemellus muscles to penetrate and innervate the quadratus femoris. It supplies a small branch to the gemellus inferior.
+
+Nerve to obturator internus
+The nerve to the obturator internus enters the gluteal region  through  the  greater  sciatic  foramen  inferior  to the piriformis muscle and between the posterior cutane-ous nerve of the thigh and the pudendal nerve (Fig. 6.48). It  supplies  a  small  branch  to  the  gemellus  superior and  then  passes  over  the  ischial  spine  and  through the  lesser  sciatic  foramen  to  innervate  the  obturator internus muscle from the medial surface of the muscle in the perineum.
+
+Posterior cutaneous nerve of the thigh
+The posterior cutaneous nerve of  the thigh enters the gluteal region through the greater sciatic foramen inferior to the piriformis muscle and immediately medial to the sciatic nerve (Fig. 6.48). It descends through the gluteal
+
+region just deep to the gluteus maximus and enters the posterior thigh.
+The  posterior  cutaneous  nerve  of  the  thigh  has  a number of gluteal branches, which loop around the lower margin of the gluteus maximus muscle to innervate skin over the gluteal fold. A small perineal branch passes medi-ally to contribute to the innervation of  the skin of  the scrotum or labia majora in the perineum. The main trunk of the posterior cutaneous nerve of the thigh passes infe-riorly, giving rise to branches that innervate the skin on the posterior thigh and leg.
+
+Pudendal nerve
+The pudendal nerve enters the gluteal region through the greater sciatic foramen inferior to the piriformis muscle and medial to the sciatic nerve (Fig. 6.48). It passes over the sacrospinous ligament and immediately passes through the lesser sciatic foramen to enter the perineum. The course of the pudendal nerve in the gluteal region is short and the nerve is often hidden by the overlying upper margin of the sacrotuberous ligament.
+The pudendal nerve is the major somatic nerve of the perineum and has no branches in the gluteal region.
+
+Inferior gluteal nerve
+The  inferior  gluteal  nerve  enters  the  gluteal  region through the greater sciatic foramen inferior to the pirifor-mis muscle and along the posterior surface of the sciatic nerve (Fig. 6.48). It penetrates and supplies the gluteus maximus muscle.
+
+Perforating cutaneous nerve
+The perforating cutaneous nerve is the only nerve in the gluteal region that does not enter the area through the greater sciatic foramen. It is a small nerve that leaves the sacral plexus in the pelvic cavity by piercing the sacro-tuberous ligament. It then loops around the lower border of the gluteus maximus to supply the skin over the medial aspect of the gluteus maximus (Fig. 6.48).
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+572
+Regional Anatomy  •  Gluteal Region	6
+
+
+
+In the clinic
+
+Intramuscular injections
+From time to time it is necessary to administer drugs intramuscularly, that is, by direct injection into muscles. This procedure must be carried out without injuring neurovascular structures. A typical site for an intramuscular injection is the gluteal region. The sciatic nerve passes through this region and needs to be avoided. The safest place to inject is the upper outer quadrant of either gluteal region.
+The gluteal region can be divided into quadrants by two imaginary lines positioned using palpable bony landmarks (Fig. 6.49). One line descends vertically from the highest point of the iliac crest. Another line is horizontal and passes through the first line midway between the highest point of the iliac crest and the horizontal plane through the ischial tuberosity.
+It is important to remember that the gluteal region extends as far forward as the anterior superior iliac spine. The sciatic nerve curves through the upper lateral corner of the lower medial quadrant and descends along the medial margin of the lower lateral quadrant.
+Occasionally, the sciatic nerve bifurcates into its tibial and common fibular branches in the pelvis, in which case the common fibular nerve passes into the gluteal region through, or even above, the piriformis muscle.
+The superior gluteal nerve and vessels normally enter the gluteal region above the piriformis and pass superiorly and forward.
+The anterior corner of the upper lateral quadrant is normally used for injections to avoid injuring any part of the sciatic nerve or other nerves and vessels in the gluteal region. A needle placed in this region enters the gluteus medius anterosuperior to the margin of the gluteus maximus.
+
+
+
+Vertical line	Highest point on iliac crest
+
+
+Safe injection site
+
+Upper medial                                                     Upper lateral quadrant                                                     quadrant
+
+Horizontal line
+
+
+Lower medial                                                     Lower lateral quadrant                                                     quadrant
+
+
+Plane through ischial
+Ischial	tuberosity tuberosity
+
+
+
+Gluteal fold
+
+
+
+
+Fig. 6.49  Site for intramuscular injections in the gluteal region.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+573
+Lower Limb
+
+
+Arteries
+Two arteries enter the gluteal region from the pelvic cavity through the greater sciatic foramen, the inferior gluteal artery and the superior gluteal artery (Fig. 6.50). They supply structures in the gluteal region and posterior thigh and have important collateral anastomoses with branches of the femoral artery.
+
+
+Superior gluteal artery
+The superior gluteal artery originates from the posterior trunk of  the internal iliac artery in the pelvic cavity. It leaves the pelvic cavity with the superior gluteal nerve through the greater sciatic foramen above the piriformis muscle (Fig. 6.50). In the gluteal region, it divides into a superficial branch and a deep branch:
+
+
+
+Inferior gluteal artery
+The inferior gluteal artery originates from the anterior trunk of  the internal iliac artery in the pelvic cavity. It leaves the pelvic cavity with the inferior gluteal nerve through the greater sciatic foramen inferior to the pirifor-mis muscle (Fig. 6.50).
+
+
+■     The superficial branch passes onto the deep surface of the gluteus maximus muscle.
+■     The deep branch passes between the gluteus medius and minimus muscles.
+
+In addition to adjacent muscles, the superior gluteal
+
+
+
+The inferior gluteal artery supplies adjacent muscles and descends through the gluteal region and into the posterior thigh where it supplies adjacent structures and anastomoses  with  perforating  branches  of  the  femoral artery. It also supplies a branch to the sciatic nerve.
+
+artery contributes to the supply of the hip joint. Branches of the artery also anastomose with the lateral and medial femoral circumflex arteries from the deep femoral artery in the thigh, and with the inferior gluteal artery (Fig. 6.51).
+
+
+
+
+
+
+Superficial branch
+
+
+Deep branch	Superior gluteal artery
+
+Inferior gluteal artery
+
+
+
+
+
+Superior gluteal artery and vein
+Piriformis muscle
+Lateral femoral circumflex artery
+
+
+Medial femoral circumflex artery
+
+Lateral femoral circumflex artery
+
+Medial femoral circumflex artery
+
+Deep artery of thigh
+
+First perforating artery
+Femoral artery
+
+Second perforating artery
+
+
+
+Third perforating artery
+
+Inferior gluteal artery and vein
+
+
+
+First perforating artery from deep artery of thigh
+
+574	Fig. 6.50  Arteries of the gluteal region.
+
+
+
+Fig. 6.51  Anastomoses between gluteal arteries and vessels originating from the femoral artery in the thigh. Posterior view.
+Regional Anatomy  •  Thigh	6
+
+
+
+
+Veins
+Inferior and superior gluteal veins follow the inferior and superior gluteal arteries into the pelvis where they join the pelvic plexus of veins. Peripherally, the veins anastomose with  superficial  gluteal  veins,  which  ultimately  drain anteriorly into the femoral vein.
+
+■     Anteriorly, it is separated from the abdominal wall by the inguinal ligament.
+■     Posteriorly, it is separated from the gluteal region by the gluteal fold superficially, and by the inferior margins of  the  gluteus  maximus  and  quadratus  femoris  on deeper planes.
+
+
+
+
+Lymphatics
+Deep lymphatic vessels of  the gluteal region accompany
+
+Structures enter and leave the top of the thigh by three routes:
+
+
+
+the blood vessels into the pelvic cavity and connect with internal iliac nodes.
+Superficial lymphatics drain into the superficial inguinal nodes on the anterior aspect of the thigh.
+
+THIGH
+
+The thigh is the region of the lower limb that is approxi-mately between the hip and knee joints (Fig. 6.52):
+
+■     Posteriorly, the thigh is continuous with the gluteal region and the major structure passing between the two regions is the sciatic nerve.
+■     Anteriorly, the thigh communicates with the abdominal cavity through the aperture between the inguinal liga-ment and pelvic bone, and major structures passing through this aperture are the iliopsoas and pectineus muscles; the femoral nerve, artery, and vein; and lym-phatic vessels.
+
+
+
+
+
+
+
+
+
+Inferior margin of gluteus maximus
+
+Gap between inguinal ligament Abdominal wall	and pelvic bone
+
+Anterior superior iliac spine
+
+Inguinal ligament
+
+
+
+Quadratus femoris
+
+Pubic tubercle
+Gluteal fold	Sciatic nerve
+
+
+Obturator canal
+
+Anterior
+
+
+Anterior compartment
+
+
+
+
+
+Medial
+
+Medial
+Popliteal fossa	compartment
+
+C	Posterior
+
+Popliteal fossa (posterior to knee)
+
+
+Lateral
+
+
+
+Posterior compartment
+
+
+
+
+
+
+
+
+
+A	B
+
+Fig. 6.52  Thigh. A. Posterior view. B. Anterior view. C. Cross section through the midthigh.	575
+Lower Limb
+
+
+
+■     Medially, structures (including the obturator nerve and associated vessels) pass between the thigh and pelvic cavity through the obturator canal.
+
+The thigh is divided into three compartments by inter-
+
+In proximal and distal regions of the femur, the linea aspera widens to form an additional posterior surface. At the distal end of the femur, this posterior surface forms the floor of the popliteal fossa, and its margins form the medial and lateral supracondylar lines. The medial supracon-
+
+muscular septa between the posterior aspect of the femur	dylar line terminates at a prominent tubercle (the adduc-and the fascia lata (the thick layer of  deep fascia that	tor  tubercle)  on  the  superior  aspect  of  the  medial completely surrounds or invests the thigh; Fig. 6.52C):	condyle of the distal end. Just lateral to the lower end of
+
+
+■     The anterior compartment of  the thigh contains muscles that mainly extend the leg at the knee joint.
+■     The posterior compartment of  the thigh contains muscles that mainly extend the thigh at the hip joint and flex the leg at the knee joint.
+■     The  medial  compartment  of  the  thigh  consists of  muscles that mainly adduct the thigh at the hip joint.
+
+The sciatic nerve innervates muscles in the posterior
+
+the medial supracondylar line is an elongate roughened area of bone for the proximal attachment of the medial head of the gastrocnemius muscle (Fig. 6.52).
+The distal end of the femur is characterized by two large condyles, which articulate with the proximal head of the tibia. The condyles are separated posteriorly by an inter-condylar  fossa  and  are  joined  anteriorly  where  they articulate with the patella.
+The surfaces of  the condyles that articulate with the tibia are rounded posteriorly and become flatter inferiorly. On each condyle, a shallow oblique groove separates the
+
+
+
+compartment of the thigh, the femoral nerve innervates muscles in the anterior compartment of the thigh, and the obturator nerve innervates most muscles in the medial compartment of the thigh.
+The major artery, vein, and lymphatic channels enter the thigh anterior to the pelvic bone and pass through the femoral triangle inferior to the inguinal ligament. Vessels and nerves passing between the thigh and leg pass through the popliteal fossa posterior to the knee joint.
+
+surface that articulates with the tibia from the more ante-rior surface that articulates with the patella. The surfaces of  the medial and lateral condyles that articulate with the patella form a V-shaped trench, which faces anteriorly. The lateral surface of  the trench is larger and steeper than the medial surface.
+The walls of the intercondylar fossa bear two facets for the superior attachment of the cruciate ligaments, which stabilize the knee joint (Fig. 6.53):
+
+
+
+
+Bones
+The skeletal support for the thigh is the femur. Most of the large muscles in the thigh insert into the proximal ends of the two bones of  the leg (tibia and fibula) and flex and extend the leg at the knee joint. The distal end of the femur provides origin for the gastrocnemius muscles, which are predominantly in the posterior compartment of the leg and plantarflex the foot.
+
+■     The wall formed by the lateral surface of  the medial condyle has a large oval facet, which covers most of the inferior half of the wall, for attachment of the proximal end of the posterior cruciate ligament.
+■     The wall formed by the medial surface of  the lateral condyle has a posterosuperior smaller oval facet for attachment of the proximal end of the anterior cruci-ate ligament.
+
+
+
+
+Shaft and distal end of femur
+The shaft of the femur is bowed forward and has an oblique course from the neck of the femur to the distal end (Fig.
+
+Epicondyles, for the attachment of collateral ligaments of the knee joint, are bony elevations on the nonarticular outer surfaces of the condyles (Fig. 6.53). Two facets sepa-rated  by  a  groove  are  just  posterior  to  the  lateral
+
+6.53).  As  a  consequence  of  this  oblique  orientation,	epicondyle:
+
+the knee is close to the midline under the body’s center of gravity.
+The middle part of the shaft of the femur is triangular in cross section (Fig. 6.53D). In the middle part of the shaft, the  femur  has  smooth  medial  (posteromedial),  lateral (posterolateral), and anterior surfaces and medial, lateral, and posterior borders. The medial and lateral borders are
+
+
+■     The upper facet is for attachment of  the lateral head of the gastrocnemius muscle.
+■     The inferior facet is for attachment of  the popliteus muscle.
+
+The tendon of the popliteus muscle lies in the groove
+
+rounded,  whereas  the  posterior  border  forms  a  broad	separating the two facets. 576	roughened crest—the linea aspera.
+Regional Anatomy  •  Thigh	6
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Posterior surface
+
+
+
+Anterior surface
+
+Lateral     D               Medial border                             border
+
+
+Lateral (posterolateral) surface
+
+Medial	Linea aspera (posteromedial)
+surface
+
+Linea aspera
+
+
+Adductor tubercle
+
+Facet for attachment of lateral head of gastrocnemius
+
+Medial epicondyle
+
+
+Lateral supracondylar line
+
+Medial supracondylar line
+
+Facet for attachment of lateral head of gastrocnemius muscle
+Lateral condyle
+
+
+Roughened area for attachment of medial head
+of gastrocnemius muscle
+
+Adductor tubercle
+
+
+
+
+
+Lateral epicondyle
+
+
+
+A
+
+
+
+Facet for attachment of the tendon of popliteus muscle
+
+
+B
+
+
+Facet for attachment of the tendon of popliteus muscle
+Lateral
+epicondyle
+Patellar surface
+Facet for attachment of anterior cruciate ligament
+Intercondylar fossa
+C
+
+Medial condyle
+
+Facet for attachment of posterior cruciate ligament
+
+
+Fig. 6.53  Shaft and distal end of femur. A. Lateral view. B. Anterior view. C. Posterior view. D. Cross section through shaft of femur.
+
+
+
+
+
+
+
+
+577
+Lower Limb
+
+
+
+The medial epicondyle is a rounded eminence on the medial surface of the medial condyle. Just posterosuperior to the medial epicondyle is the adductor tubercle.
+
+Patella
+The patella (knee cap) is the largest sesamoid bone (a bone formed within the tendon of a muscle) in the body and is formed within the tendon of the quadriceps femoris muscle as it crosses anterior to the knee joint to insert on the tibia.
+
+The patella is triangular:
+
+■     Its  apex  is  pointed  inferiorly  for  attachment  to  the patellar ligament, which connects the patella to the tibia (Fig. 6.54).
+■     Its base is broad and thick for the attachment of  the quadriceps tendon from above.
+■     Its posterior surface articulates with the femur and has medial and lateral facets, which slope away from a raised smooth ridge—the lateral facet is larger than the medial facet for articulation with the larger correspond-ing surface on the lateral condyle of the femur.
+
+
+
+
+
+
+
+
+
+
+
+Quadriceps
+tendon	Patella
+
+
+Lateral	Medial	Lateral	Distal end of femur
+
+Lateral	Medial
+
+Patellar ligament
+A	B	C
+
+Fig. 6.54  Patella. A. Anterior view. B. Posterior view. C. Superior view.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+578
+Regional Anatomy  •  Thigh	6
+
+
+
+
+Proximal end of tibia
+The tibia is the medial and larger of the two bones in the leg, and is the only one that articulates with the femur at the knee joint.
+The proximal end of the tibia is expanded in the trans-verse plane for weight-bearing and consists of a medial condyle and a lateral condyle, which are both flattened in the horizontal plane and overhang the shaft (Fig. 6.55). The superior surfaces of the medial and lateral condyles are articular and separated by an intercondylar region, which contains sites of attachment for strong ligaments (cruciate ligaments) and interarticular cartilages (menisci)
+of the knee joint.
+
+The articular surfaces of the medial and lateral condyles and  the  intercondylar  region  together  form  a  “tibial plateau,” which articulates with and is anchored to the distal end of  the femur. Inferior to the condyles on the proximal part of the shaft is a large tibial tuberosity and roughenings for muscle and ligament attachments.
+
+Tibial condyles and intercondylar areas
+The  tibial  condyles  are  thick  horizontal  discs  of  bone attached to the top of the tibial shaft (Fig. 6.55).
+The medial condyle is larger than the lateral condyle and is better supported over the shaft of the tibia. Its supe-rior surface is oval for articulation with the medial condyle
+
+
+
+
+Intercondylar region
+
+
+Attachment of posterior cruciate ligament
+
+Posterior attachment of lateral meniscus
+
+Area of articulation with lateral meniscus
+
+Posterior attachment of medial meniscus
+
+Area of articulation with medial meniscus
+
+Tubercles of intercondylar eminence
+
+
+
+
+Anterior attachment of lateral meniscus
+
+A	Roughened and perforated area
+
+Attachment of anterior cruciate ligament
+
+
+Anterior attachment of medial meniscus
+Tuberosity
+
+
+
+
+
+
+Lateral condyle
+
+
+Tibial tuberosity
+
+
+Tubercles of intercondylar eminence
+
+Anterior attachment of
+medial meniscus
+Groove Medial condyle
+
+Roughened and perforated area
+
+Attachment of medial meniscus Attachment of posterior cruciate ligament
+
+
+Articular facet for proximal head of fibula
+
+
+Site of attachment of sartorius, gracilis, and semitendinosus muscles
+
+
+Shaft of tibia
+
+
+
+
+
+
+
+
+
+B
+
+
+
+
+
+Lateral surface
+
+Interosseous border
+
+
+Anterior Anterior border
+D
+
+
+
+
+
+Posterior surface
+Posterior
+
+Soleal line
+
+
+
+
+
+Medial surface
+
+Medial border
+
+C
+
+
+Fig. 6.55  Proximal end of the tibia. A. Superior view, tibial plateau. B. Anterior view. C. Posterior view. D. Cross section through the shaft
+of tibia.	579
+Lower Limb
+
+
+
+of the femur. The articular surface extends laterally onto the side of the raised medial intercondylar tubercle.
+The superior surface of the lateral condyle is circular and articulates above with the lateral condyle of the femur. The medial edge of this surface extends onto the side of the lateral intercondylar tubercle.
+The superior articular surfaces of both the lateral and medial condyles are concave, particularly centrally. The outer margins of the surfaces are flatter and are the regions in contact with the interarticular discs (menisci) of fibro-cartilage in the knee joint.
+
+numerous small nutrient foramina for blood vessels. This region is continuous with a similar surface on the front of the tibia above the tuberosity and lies against infrapatellar connective tissue.
+
+Tibial tuberosity
+The tibial tuberosity is a palpable inverted triangular area on the anterior aspect of the tibia below the site of junction between the two condyles (Fig. 6.55). It is the site of  attachment  for  the  patellar  ligament,  which  is  a continuation of the quadriceps femoris tendon below the
+
+The  nonarticular  posterior  surface  of   the  medial	patella.
+
+condyle bears a distinct horizontal groove for part of the attachment  of  the  semimembranosus  muscle,  and  the
+
+
+Shaft of tibia
+
+undersurface  of   the  lateral  condyle  bears  a  distinct	The shaft of the tibia is triangular in cross section and has
+
+circular facet for articulation with the proximal head of the fibula.
+
+three surfaces (posterior, medial, and lateral) and three borders (anterior, interosseous, and medial) (Fig. 6.55D):
+
+The  intercondylar  region  of  the  tibial  plateau  lies between the articular surfaces of  the medial and lateral condyles (Fig. 6.55). It is narrow centrally where it is raised to form the intercondylar eminence, the sides of which are elevated further to form medial and lateral intercondy-lar tubercles.
+The intercondylar region bears six distinct facets for the attachment of menisci and cruciate ligaments. The ante-rior intercondylar area widens anteriorly and bears three facets:
+
+
+■     The anterior border is sharp and descends from the tibial tuberosity where it is continuous superiorly with a ridge that passes along the lateral margin of  the tuberosity and onto the lateral condyle.
+■     The interosseous border is a subtle vertical ridge that descends along the lateral aspect of the tibia from the region of  bone anterior and inferior to the articular facet for the head of the fibula.
+■     The  medial  border  is  indistinct  superiorly  where  it begins at the anterior end of the groove on the posterior
+
+
+
+■     The most anterior facet is for attachment of the anterior end (horn) of the medial meniscus.
+■     Immediately posterior to the most anterior facet is a facet  for  the  attachment  of   the  anterior  cruciate ligament.
+■     A small facet for the attachment of  the anterior end (horn) of the lateral meniscus is just lateral to the site of attachment of the anterior cruciate ligament.
+
+The  posterior  intercondylar  area  also  bears  three
+
+surface of  the medial tibial condyle, but is sharp in midshaft.
+
+The large medial surface of  the shaft of  the tibia, between the anterior and medial borders, is smooth and subcutaneous,  and  is  palpable  along  almost  its  entire extent. Medial and somewhat inferior to the tibial tuberos-ity, this medial surface bears a subtle, slightly roughened elongate elevation. This elevation is the site of the combined attachment of three muscles (sartorius, gracilis, and semi-
+
+attachment facets:	tendinosus), which descend from the thigh.
+
+
+■     The most anterior is for attachment of  the posterior horn of the lateral meniscus.
+■     Posteromedial  to  the  most  anterior  facet  is  the  site of  attachment for the posterior horn of  the medial meniscus.
+■     Behind the site of attachment for the posterior horn of the medial meniscus is a large facet for the attachment of the posterior cruciate ligament.
+
+In addition to these six sites of attachment for menisci
+
+The  posterior  surface  of   the  shaft  of   the  tibia, between the interosseous and medial borders, is widest superiorly where it is crossed by a roughened oblique line (the soleal line).
+The lateral surface, between the anterior and interos-seous borders, is smooth and unremarkable.
+
+Proximal end of fibula
+The fibula is the lateral bone of the leg and does not take part in formation of the knee joint or in weight-bearing. It is much smaller than the tibia and has a small proximal
+
+
+
+and cruciate ligaments, a large anterolateral region of the 580	anterior intercondylar area is roughened and perforated by
+
+head, a narrow neck, and a delicate shaft, which ends as the lateral malleolus at the ankle.
+Regional Anatomy  •  Thigh	6
+
+
+
+The head of the fibula is a globe-shaped expansion at the proximal end of the fibula (Fig. 6.56). A circular facet on the superomedial surface is for articulation above with a similar facet on the inferior aspect of the lateral condyle of the tibia. Just posterolateral to this facet, the bone pro-
+
+■     The posterior border is rounded and descends from the region of the styloid process of the head.
+■     The interosseous border is medial in position.
+
+The three surfaces of the fibula are associated with the
+
+
+
+jects superiorly as a blunt apex (styloid process).
+The lateral surface of the head of the fibula bears a large impression for the attachment of the biceps femoris muscle. A depression near the upper margin of this impression is for attachment of  the fibular collateral ligament of  the knee joint.
+The neck of  the fibula separates the expanded head from the shaft. The common fibular nerve lies against the posterolateral aspect of the neck.
+Like the tibia, the shaft of the fibula has three borders (anterior, posterior, and interosseous) and three surfaces (lateral,  posterior,  and  medial),  which  lie  between  the borders (Fig. 6.56):
+
+three  muscular  compartments  (lateral,  posterior,  and anterior) of the leg.
+
+
+Muscles
+Muscles of the thigh are arranged in three compartments separated by intermuscular septa (Fig. 6.57).
+The anterior compartment of  the thigh contains the sartorius and the four large quadriceps femoris muscles (rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius). All are innervated by the femoral nerve. In addition, the terminal ends of  the psoas major and iliacus muscles pass into the upper part of  the anterior compartment from sites of origin on the posterior abdomi-
+
+
+
+■     The anterior  border is sharp midshaft and begins superiorly from the anterior aspect of the head.
+
+
+
+Apex
+
+nal wall. These muscles are innervated by branches directly from  the  anterior  rami  of  L1  to  L3  (psoas  major)  or from the femoral nerve (iliacus) as it passes down the abdominal wall.
+The medial compartment of the thigh contains six muscles (gracilis, pectineus, adductor longus, adductor
+
+
+
+Attachment site for fibular collateral ligament of knee
+
+Attachment site for tendon of biceps femoris muscle
+
+
+Common fibular nerve
+
+
+Lateral surface
+Anterior border
+
+Medial surface
+
+Interosseous border
+
+
+Facet for articulation with inferior surface of lateral condyle
+of tibia
+
+
+Head
+
+
+
+Neck
+
+brevis,  adductor  magnus,  and  obturator  externus).  All except the pectineus, which is innervated by the femoral nerve, and part of the adductor magnus, which is inner-vated by the sciatic nerve, are innervated by the obturator nerve.
+The posterior compartment of  the thigh contains three  large  muscles  termed  the  “hamstrings.”  All  are innervated by the sciatic nerve.
+
+
+
+
+Anterior
+
+Anterior compartment
+
+
+
+
+B
+
+Posterior border
+
+
+
+
+A
+
+
+Medial crest on posterior surface
+
+Posterior surface
+
+Lateral surface
+
+
+Medial surface
+
+Shaft
+
+
+
+
+
+Medial part of posterior surface
+
+
+Lateral
+Linea aspera
+
+Deep fascia
+
+Posterior compartment
+Intermuscular septae
+Posterior
+
+
+Medial
+
+
+
+Medial compartment
+
+Fig. 6.56  Proximal end of the fibula. A. Anterior view.
+B. Cross section through the shaft of fibula.	Fig. 6.57  Transverse section through the midthigh.	581
+Lower Limb
+
+
+
+In the clinic
+
+Compartment syndrome
+Compartment syndrome occurs when there is swelling within a fascial enclosed muscle compartment in
+the limbs. Typical causes include limb trauma, intracompartment hemorrhage, and limb compression. As pressure within the compartment elevates, capillary blood flow and tissue perfusion is compromised, which can ultimately lead to neuromuscular damage if not treated.
+
+
+Anterior compartment
+Muscles in the anterior compartment (Table 6.3) act on the hip and knee joints:
+
+■     the psoas major and iliacus act on the hip joint,
+■     the sartorius and rectus femoris act on both the hip and knee joints, and
+■     the vastus muscles act on the knee joint.
+
+
+
+
+
+
+
+
+Table 6.3    Muscles of the anterior compartment of thigh (spinal segments in bold are the major segments innervating the muscle)
+
+
+Muscle Psoas major
+
+
+
+Iliacus
+
+Vastus medialis
+
+
+
+Vastus intermedius
+
+
+Vastus lateralis
+
+
+
+
+Rectus femoris
+
+
+
+Sartorius
+
+Origin
+Posterior abdominal wall (lumbar transverse processes, intervertebral discs, and adjacent bodies from TXII to LV and tendinous arches between these points)
+Posterior abdominal wall (iliac fossa)
+
+Femur—medial part of intertrochanteric line, pectineal line, medial lip of the linea aspera, medial supracondylar line
+Femur—upper two-thirds of anterior and lateral surfaces
+
+Femur—lateral part of intertrochanteric line, margin of greater trochanter, lateral margin of gluteal tuberosity, lateral lip of the linea aspera
+Straight head originates from the anterior inferior iliac spine; reflected head originates from the ilium just superior to the acetabulum
+Anterior superior iliac spine
+
+Insertion
+Lesser trochanter of femur
+
+
+
+
+Lesser trochanter of femur
+
+Quadriceps femoris tendon and medial border of patella
+
+
+Quadriceps femoris tendon, lateral margin of patella, and lateral condyle of tibia
+Quadriceps femoris tendon and lateral margin of patella
+
+
+
+Quadriceps femoris tendon
+
+
+
+Medial surface of tibia just inferomedial to tibial tuberosity
+
+Innervation
+Anterior rami (L1, L2, L3)
+
+
+
+Femoral nerve (L2, L3)
+Femoral nerve (L2, L3, L4)
+
+
+Femoral nerve (L2, L3, L4)
+
+Femoral nerve (L2, L3, L4)
+
+
+
+Femoral nerve (L2, L3, L4)
+
+
+Femoral nerve (L2, L3)
+
+Function
+Flexes the thigh at the hip joint
+
+
+
+Flexes the thigh at the hip joint
+Extends the leg at the knee joint
+
+
+Extends the leg at the knee joint
+
+Extends the leg at the knee joint
+
+
+
+Flexes the thigh at the hip joint and extends the leg at the knee joint
+
+Flexes the thigh at the hip joint and flexes the leg at the knee joint
+
+
+
+
+
+
+
+
+
+
+
+
+
+582
+Regional Anatomy  •  Thigh	6
+
+
+
+
+Iliopsoas—psoas major and iliacus
+The psoas major and iliacus muscles originate on the posterior abdominal wall and descend into the upper part of  the anterior compartment of  the thigh through the lateral half of the gap between the inguinal ligament and the pelvic bone (Fig. 6.58).
+Although the iliacus and psoas major originate as sepa-rate muscles in the abdomen, both insert by a common
+
+tendon onto the lesser trochanter of the femur and together are usually referred to as the iliopsoas muscle.
+The iliopsoas is a powerful flexor of the thigh at the hip joint and can also contribute to lateral rotation of  the thigh. The psoas major is innervated by branches from the anterior rami of L1 to L3 and the iliacus is innervated by branches from the femoral nerve in the abdomen.
+
+
+
+
+
+
+
+TXII
+
+
+LI
+
+
+LII
+
+
+Psoas major	LIII
+
+
+LIV
+
+Iliacus
+LV
+Anterior superior iliac spine
+
+
+Anterior inferior iliac spine Inguinal ligament
+
+
+
+
+
+
+
+
+Lesser trochanter
+
+
+
+Fig. 6.58  Psoas major and iliacus muscles.
+
+
+
+
+
+
+
+
+583
+Lower Limb
+
+
+
+
+Quadriceps femoris—vastus medialis, intermedius, and lateralis and rectus femoris
+The large quadriceps femoris muscle consists of three vastus muscles (vastus medialis, vastus intermedius, and vastus lateralis) and the rectus femoris muscle (Fig. 6.59). The quadriceps femoris muscle mainly extends the leg
+at the knee joint, but the rectus femoris component also assists flexion of  the thigh at the hip joint. Because the
+
+vastus muscles insert into the margins of the patella as well as into the quadriceps femoris tendon, they stabilize the position of the patella during knee joint movement.
+The quadriceps femoris is innervated by the femoral nerve with contributions mainly from spinal segments L3 and L4. A tap with a tendon hammer on the patellar liga-ment therefore tests reflex activity mainly at spinal cord levels L3 and L4.
+
+
+
+
+
+
+
+
+
+
+Sartorius
+
+Reflected head of rectus femoris
+
+Straight head of rectus femoris
+
+
+
+
+Vastus lateralis
+
+Vastus intermedius
+
+Vastus medialis
+
+Vastus lateralis
+
+Medial compartment of thigh
+
+Posterior compartment of thigh	Rectus femoris
+
+
+Vastus lateralis
+
+Vastus intermedius
+Rectus femoris
+Vastus medialis
+
+Adductor canal
+Sartorius
+
+Articularis genus
+
+
+
+Sartorius
+
+
+
+Vastus medialis
+
+
+
+Suprapatellar bursa
+
+Quadriceps femoris tendon
+
+
+
+Patellar ligament
+
+Tibial tuberosity
+
+
+Quadriceps femoris tendon
+
+Patella
+
+
+Patellar ligament
+
+Pes anserinus
+
+
+
+Attachment of pes anserinus
+
+Sartorius Gracilis Semitendinosus
+
+
+584	Fig. 6.59  Muscles of the anterior compartment of thigh.
+Regional Anatomy  •  Thigh	6
+
+
+Vastus muscles
+The vastus muscles originate from the femur, whereas the rectus femoris muscle originates from the pelvic bone. All attach first to the patella by the quadriceps femoris tendon and then to the tibia by the patellar ligament.
+
+
+■     the other from a roughened area of the ilium immedi-ately  superior  to  the  acetabulum  (reflected  head) (Fig. 6.59).
+
+The two heads of the rectus femoris unite to form an
+
+
+
+The vastus medialis originates from a continuous line of attachment on the femur, which begins anteromedially on the intertrochanteric line and continues posteroinferi-orly along the pectineal line and then descends along the medial lip of the linea aspera and onto the medial supra-condylar line. The fibers converge onto the medial aspect of the quadriceps femoris tendon and the medial border of the patella (Fig. 6.59).
+The vastus intermedius originates mainly from the upper two-thirds of the anterior and lateral surfaces of the femur and the adjacent intermuscular septum (Fig. 6.59). It merges into the deep aspect of the quadriceps femoris tendon and also attaches to the lateral margin of  the patella and lateral condyle of the tibia.
+A tiny muscle (articularis genus) originates from the femur just inferior to the origin of the vastus intermedius and inserts into the suprapatellar bursa associated with the knee joint (Fig. 6.59). This articular muscle, which is often part of  the vastus intermedius muscle, pulls the bursa away from the knee joint during extension.
+The vastus lateralis is the largest of the vastus muscles (Fig. 6.59). It originates from a continuous line of attach-ment, which begins anterolaterally from the superior part of the intertrochanteric line of the femur and then circles laterally around the bone to attach to the lateral margin of the gluteal tuberosity and continues down the upper part of the lateral lip of the linea aspera. Muscle fibers converge mainly onto the quadriceps femoris tendon and the lateral margin of the patella.
+
+Rectus femoris
+Unlike the vastus muscles, which cross only the knee joint, the rectus femoris muscle crosses both the hip and the knee joints (Fig. 6.59).
+The rectus femoris has two tendinous heads of origin from the pelvic bone:
+
+elongate muscle belly, which lies anterior to the vastus intermedius muscle and between the vastus lateralis and vastus medialis muscles, to which it is attached on either side. At the distal end, the rectus femoris muscle converges on the quadriceps femoris tendon and inserts on the base of the patella.
+
+Patellar ligament
+The patellar ligament is functionally the continuation of the quadriceps femoris tendon below the patella and is attached above to the apex and margins of the patella and below to the tibial tuberosity (Fig. 6.59). The more super-ficial fibers of the quadriceps femoris tendon and the patel-lar ligament are continuous over the anterior surface of the patella, and lateral and medial fibers are continuous with the ligament beside the margins of the patella.
+
+Sartorius
+The sartorius muscle is the most superficial muscle in the anterior compartment of the thigh and is a long strap-like muscle that descends obliquely through the thigh from the anterior superior iliac spine to the medial surface of the proximal shaft of the tibia (Fig. 6.59). Its flat aponeurotic insertion into the tibia is immediately anterior to the inser-tion of the gracilis and semitendinosus muscles.
+The  sartorius,  gracilis,  and  semitendinosus  muscles attach to the tibia in a three-pronged pattern on the tibia, so their combined tendons of insertion are often termed the pes anserinus (Latin for “goose foot”).
+In the upper one-third of the thigh, the medial margin of the sartorius forms the lateral margin of the femoral triangle.
+In the middle one-third of the thigh, the sartorius forms the anterior wall of the adductor canal.
+The sartorius muscle assists in flexing the thigh at the hip joint and the leg at the knee joint. It also abducts the thigh and rotates it laterally, as when resting the foot on
+
+
+
+■     one  from  the  anterior  inferior  iliac  spine  (straight head), and
+
+the opposite knee when sitting.
+The sartorius is innervated by the femoral nerve.
+
+
+
+
+
+
+
+
+
+585
+Lower Limb
+
+
+
+
+Medial compartment
+There are six muscles in the medial compartment of the thigh  (Table  6.4):  gracilis,  pectineus,  adductor  longus, adductor brevis, adductor magnus, and obturator externus (Fig. 6.60). Collectively, all these muscles except the obtu-rator externus mainly adduct the thigh at the hip joint; the adductor  muscles  may  also  medially  rotate  the  thigh. Obturator externus is a lateral rotator of the thigh at the hip joint.
+
+
+Gracilis
+The gracilis is the most superficial of the muscles in the medial compartment of thigh and descends almost verti-cally down the medial side of the thigh (Fig. 6.60). It is attached above to the outer surface of  the ischiopubic ramus of the pelvic bone and below to the medial surface of the proximal shaft of the tibia, where it lies sandwiched between the tendon of sartorius in front and the tendon of the semitendinosus behind.
+
+
+
+
+
+
+
+
+Table 6.4    Muscles of the medial compartment of thigh (spinal segments in bold are the major segments innervating the muscle)
+
+
+Muscle Gracilis
+
+
+
+Pectineus
+
+
+
+Adductor longus
+
+
+
+Adductor brevis
+
+
+Adductor magnus
+
+
+
+
+Obturator externus
+
+Origin
+A line on the external surfaces of the body of the pubis, the inferior pubic ramus, and the ramus of the ischium
+Pectineal line (pecten pubis) and adjacent bone of pelvis
+
+
+External surface of body of pubis (triangular depression inferior to pubic crest and lateral to pubic symphysis)
+External surface of body of pubis and inferior pubic ramus
+
+Adductor part—ischiopubic ramus
+
+Hamstring part—ischial tuberosity
+External surface of obturator membrane and adjacent bone
+
+Insertion
+Medial surface of proximal shaft of tibia
+
+
+Oblique line extending from base of lesser trochanter to linea aspera on posterior surface of proximal femur
+Linea aspera on middle one-third of shaft of femur
+
+
+Posterior surface of proximal femur and upper one-third of linea aspera
+Posterior surface of proximal femur, linea aspera, medial supracondylar line
+Adductor tubercle and supracondylar line
+Trochanteric fossa
+
+Innervation
+Obturator nerve (L2, L3)
+
+
+
+Femoral nerve (L2, L3)
+
+
+
+Obturator nerve (anterior division) (L2, L3, L4)
+
+
+Obturator nerve (L2, L3)
+
+
+Obturator nerve (L2, L3, L4)
+
+Sciatic nerve (tibial division) (L2, L3, L4)
+Obturator nerve (posterior division) (L3, L4)
+
+Function
+Adducts thigh at hip joint and flexes leg at knee joint
+
+Adducts and flexes thigh at hip joint
+
+
+Adducts and medially rotates thigh at hip joint
+
+
+Adducts and medially rotates thigh at hip joint
+
+Adducts and medially rotates thigh at hip joint
+
+
+
+Laterally rotates thigh at hip joint
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+586
+Regional Anatomy  •  Thigh	6
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Obturator externus
+
+Adductor magnus Pectineus
+
+
+
+
+Gracilis Posterior compartment of thigh
+
+Adductor magnus
+Adductor longus
+
+Adductor brevis
+
+
+Adductor longus
+
+
+
+
+Anterior compartment of thigh
+
+Adductor canal
+
+Adductor hiatus
+
+
+
+
+
+
+
+
+Gracilis
+Sartorius attachment
+Pes anserinus
+Semitendinosus attachment
+
+Fig. 6.60  Muscles of the medial compartment of thigh. Anterior view.
+
+
+
+
+
+
+587
+Lower Limb
+
+
+
+
+Pectineus
+The pectineus is a flat quadrangular muscle (Fig. 6.61). It is attached above to the pectineal line of the pelvic bone and adjacent bone, and descends laterally to attach to an oblique line extending from the base of the lesser trochan-ter to the linea aspera on the posterior surface of the proxi-mal femur.
+From its origin on the pelvic bone, the pectineus passes into the thigh below the inguinal ligament and forms part of the floor of the medial half of the femoral triangle.
+The pectineus adducts and flexes the thigh at the hip joint and is innervated by the femoral nerve.
+
+Adductor longus
+The adductor longus is a flat fan-shaped muscle that originates  from  a  small  rough  triangular  area  on  the
+
+
+
+
+
+
+
+
+
+
+Pectineal line
+
+external surface of the body of the pubis just inferior to the pubic crest and lateral to the pubic symphysis (Fig. 6.61). It expands as it descends posterolaterally to insert via  an  aponeurosis  into  the  middle  third  of  the  linea aspera.
+The adductor longus contributes to the floor of  the femoral triangle, and its medial margin forms the medial border of the femoral triangle. The muscle also forms the proximal posterior wall of the adductor canal.
+The adductor longus adducts and medially rotates the thigh at the hip joint and is innervated by the anterior division of the obturator nerve.
+
+Adductor brevis
+The adductor brevis lies posterior to the pectineus and adductor longus. It is a triangular muscle attached at its apex to the body of the pubis and inferior pubic ramus just
+
+
+
+
+
+
+
+
+
+
+Pectineal line
+
+
+
+Pectineus
+
+
+
+Adductor brevis
+
+
+
+Adductor longus
+
+
+Adductor brevis
+
+
+
+For perforating arteries
+
+
+Adductor magnus
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+588	Fig. 6.61  Pectineus, adductor longus, and adductor brevis muscles. Anterior view.
+Regional Anatomy  •  Thigh	6
+
+
+superior to the origin of the gracilis muscle (Fig. 6.61). The muscle is attached by its expanded base via an aponeurosis to a vertical line extending from lateral to the insertion of the pectineus into the upper aspect of  the linea aspera lateral to the attachment of the adductor longus.
+The adductor brevis adducts and medially rotates the thigh at the hip joint and is innervated by the obturator nerve.
+
+
+Adductor magnus
+The adductor magnus is the largest and deepest of the muscles in the medial compartment of  the thigh (Fig. 6.62). The muscle forms the distal posterior wall of  the adductor  canal.  Like  the  adductor  longus  and  brevis muscles, the adductor magnus is a triangular or fan-shaped muscle anchored by its apex to the pelvis and attached by its expanded base to the femur.
+On the pelvis, the adductor magnus is attached along a line that extends from the inferior pubic ramus, above
+
+
+
+Obturator externus
+
+
+Adductor magnus (adductor part)
+
+
+
+Perforations for branches of deep artery of thigh
+
+the  attachments  of   the  adductor  longus  and  brevis
+
+muscles, and along the ramus of the ischium to the ischial tuberosity. The part of the muscle that originates from the ischiopubic ramus expands laterally and inferiorly to insert on the femur along a vertical line of  attachment that extends from just inferior to the quadrate tubercle and medial to the gluteal tuberosity, along the linea aspera and onto the medial supracondylar line. This lateral part of the muscle is often termed the “adductor part” of the adductor magnus.
+The medial part of the adductor magnus, often called the “hamstring part,” originates from the ischial tuberosity of the pelvic bone and descends almost vertically along the thigh to insert via a rounded tendon into the adductor tubercle on the medial condyle of the distal head of the femur. It also inserts via an aponeurosis up onto the medial supracondylar line. A large circular gap inferiorly between the hamstring and adductor parts of  the muscle is the adductor hiatus (Fig. 6.62), which allows the femoral artery and associated veins to pass between the adductor canal on the anteromedial aspect of  the thigh and the popliteal fossa posterior to the knee.
+The adductor magnus adducts and medially rotates the thigh at the hip joint. The adductor part of the muscle is innervated by the obturator nerve and the hamstring part is innervated by the tibial division of the sciatic nerve.
+
+Obturator externus
+The obturator externus is a flat fan-shaped muscle. Its expansive body is attached to the external aspect of  the
+
+
+• Terminal end of deep artery of thigh
+
+
+Adductor magnus (hamstring part)
+
+
+
+Adductor hiatus
+
+
+
+Adductor tubercle
+
+
+
+
+Fig. 6.62  Adductor magnus and obturator externus muscles. Anterior view.
+
+
+
+
+
+obturator membrane and adjacent bone (Fig. 6.62). The muscle fibers converge posterolaterally to form a tendon, which passes posterior to the hip joint and neck of  the femur to insert on an oval depression on the lateral wall of the trochanteric fossa.
+The obturator externus externally rotates the thigh at the hip joint and is innervated by the posterior branch of the obturator nerve.
+
+
+
+589
+Lower Limb
+
+
+
+
+Posterior compartment
+There are three long muscles in the posterior compartment of  the thigh: biceps femoris, semitendinosus, and semi-
+
+the knee is partly flexed, the biceps femoris can laterally rotate the leg at the knee joint.
+The long head is innervated by the tibial division of the sciatic  nerve  and  the  short  head  is  innervated  by  the
+
+membranosus  (Table  6.5)—and  they  are  collectively	common fibular division of the sciatic nerve.
+
+known as the hamstrings (Fig. 6.63). All except the short head of  the biceps femoris cross both the hip and knee joints. As a group, the hamstrings flex the leg at the knee joint and extend the thigh at the hip joint. They are also rotators at both joints.
+
+Biceps femoris
+The biceps  femoris muscle is lateral in the posterior compartment of the thigh and has two heads (Fig. 6.63):
+
+
+Semitendinosus
+The  semitendinosus  muscle  is  medial  to  the  biceps femoris muscle in the posterior compartment of the thigh (Fig. 6.63). It originates with the long head of the biceps femoris muscle from the inferomedial part of  the upper area of the ischial tuberosity. The spindle-shaped muscle belly ends in the lower half of the thigh and forms a long cord-like  tendon,  which  lies  on  the  semimembranosus
+
+
+
+
+■     The  long  head  originates  with  the  semitendinosus muscle from the inferomedial part of the upper area of the ischial tuberosity.
+■     The short head arises from the lateral lip of the linea aspera on the shaft of the femur.
+
+The muscle belly of the long head crosses the posterior
+
+muscle  and  descends  to  the  knee.  The  tendon  curves around the medial condyle of  the tibia and inserts into the medial surface of the tibia just posterior to the tendons of  the gracilis and sartorius muscles as part of  the pes anserinus.
+The  semitendinosus  flexes  the  leg  at  the  knee  joint and  extends  the  thigh  at  the  hip  joint.  Working  with the semimembranosus, it also medially rotates the thigh
+
+
+
+thigh obliquely from medial to lateral and is joined by the short head distally. Together, fibers from the two heads form a tendon, which is palpable on the lateral side of the distal thigh. The main part of  the tendon inserts into the lateral surface of  the head of  the fibula. Extensions from the tendon blend with the fibular collateral ligament and with ligaments associated with the lateral side of the knee joint.
+The biceps femoris flexes the leg at the knee joint. The long head also extends and laterally rotates the hip. When
+
+at the hip joint and medially rotates the leg at the knee joint.
+The semitendinosus muscle is innervated by the tibial division of the sciatic nerve.
+
+Semimembranosus
+The semimembranosus muscle lies deep to the semiten-dinosus muscle in the posterior compartment of the thigh (Fig. 6.63). It is attached above to the superolateral impres-sion on the ischial tuberosity and below mainly to the
+
+
+
+
+
+Table 6.5    Muscles of the posterior compartment of thigh (spinal segments in bold are the major segments innervating the muscle)
+
+
+Muscle
+Biceps femoris
+
+
+
+
+Semitendinosus
+
+
+Semimembranosus
+
+Origin
+Long head—inferomedial part of the upper area of the ischial tuberosity; short head—lateral lip of linea aspera
+Inferomedial part of the upper area of the ischial tuberosity
+Superolateral impression on the ischial tuberosity
+
+Insertion Head of fibula
+
+
+
+Medial surface of proximal tibia
+
+Groove and adjacent bone on medial and posterior surface of medial tibial condyle
+
+Innervation
+Sciatic nerve (L5, S1, S2)
+
+
+
+Sciatic nerve (L5, S1, S2)
+
+Sciatic nerve (L5, S1, S2)
+
+Function
+Flexes leg at knee joint; extends and laterally rotates thigh at hip joint and laterally rotates leg at knee joint
+
+
+Flexes leg at knee joint and extends thigh at hip joint; medially rotates thigh at hip joint and leg at knee joint
+Flexes leg at knee joint and extends thigh at hip joint; medially rotates thigh at hip joint and leg at knee joint
+
+
+
+
+
+590
+Regional Anatomy  •  Thigh	6
+
+
+
+
+
+
+
+
+
+Ischial tuberosity
+
+
+
+Quadratus femoris
+
+
+Adductor magnus
+
+Long head of biceps femoris
+
+Hamstring part of adductor magnus
+Semitendinosus
+
+
+
+Semimembranosus
+
+
+Short head of biceps femoris
+
+
+
+
+
+
+
+
+Part of semimembranosus that inserts into capsule
+around knee joint
+
+On anterior aspect of tibia attaches to pes anserinus
+
+In the clinic
+
+Muscle injuries to the lower limb
+Muscle injuries may occur as a result of direct trauma or as part of an overuse syndrome.
+Muscle injuries may occur as a minor muscle tear, which may be demonstrated as a focal area of fluid within the muscle. With increasingly severe injuries, more muscle fibers are torn and this may eventually result in a complete muscle tear. The usual muscles in the thigh that tear are the hamstring muscles. Tears in the muscles below the knee typically occur within the soleus muscle, though other muscles may be affected.
+
+Hamstring muscle injury
+Injury to the hamstring muscles is a common source of pain in athletes, particularly in those competing in sports requiring a high degree of power and speed (such as sprinting, track and field, football) where the hamstring muscles are very susceptible to injury from excessive stretching.
+The injury can range from a mild muscle strain to a complete tear of a muscle or a tendon. It usually occurs during sudden accelerations and decelerations or rapid change in direction. In adults, the most commonly injured is the muscle-tendon junction, which is a wide transition zone between the muscle and the tendon. An avulsion of the ischial tuberosity with proximal hamstring origin attachment is common in the adolescent population, particularly during sudden hip flexion because the ischial apophysis is the weakest element of the proximal hamstring unit in this age group (Fig. 6.64). Both ultrasound and MRI can be used to assess the hamstring injury with the MRI providing not only the information about the extent of the injury but also give some indication about the prognosis (future risk of re-tear, loss of function, etc).
+
+
+
+Fig. 6.63  Muscles of the posterior compartment of thigh. Posterior view.
+
+
+
+
+groove and adjacent bone on the medial and posterior surfaces of the medial tibial condyle. Expansions from the tendon also insert into and contribute to the formation of ligaments and fascia around the knee joint.
+The semimembranosus flexes the leg at the knee joint and extends the thigh at the hip joint. Working with the semitendinosus muscle, it medially rotates the thigh at the hip joint and the leg at the knee joint.
+The  semimembranosus  muscle  is  innervated  by  the tibial division of the sciatic nerve.
+
+
+
+
+
+
+
+Hamstring avulsion injury
+
+Fig. 6.64  Coronal MRI of the posterior pelvis and thigh showing a hamstring avulsion injury.
+591
+Lower Limb
+
+
+
+
+Arteries
+Three arteries enter the thigh: the femoral artery, the obturator artery, and the inferior gluteal artery. Of these, the femoral artery is the largest and supplies most of the lower limb. The three arteries contribute to an anastomotic network of vessels around the hip joint.
+
+Femoral artery
+The femoral artery is the continuation of the external iliac artery and begins as the external iliac artery passes under the inguinal ligament to enter the femoral triangle on the anterior aspect of the upper thigh (Fig. 6.65). The femoral artery is palpable in the femoral triangle just inferior to the inguinal ligament midway between the anterior superior iliac spine and the pubic symphysis.
+The femoral artery passes vertically through the femoral triangle and then continues down the thigh in the adduc-tor canal. It leaves the canal by passing through the adduc-tor hiatus in the adductor magnus muscle and becomes the popliteal artery behind the knee.
+A cluster of four small branches—superficial epigas-tric artery, superficial circumflex iliac artery, super-ficial external pudendal artery, and deep external pudendal artery—originate from the femoral artery in the femoral triangle and supply cutaneous regions of the upper thigh, lower abdomen, and perineum.
+
+Deep artery of thigh
+The largest branch of the femoral artery in the thigh is the deep  artery  of  the  thigh (profunda femoris artery), which originates from the lateral side of the femoral artery in the femoral triangle and is the major source of blood supply to the thigh (Fig. 6.65). The deep artery of the thigh immediately passes:
+
+
+Pubic symphysis
+External iliac artery
+
+
+Superficial epigastric artery
+Sartorius muscle
+
+Superficial external iliac artery
+Femoral artery
+• Midway between anterior superior iliac spine and pubic symphysis inferior to inguinal ligament
+
+Superficial external pudendal artery
+Deep external pudendal artery
+Deep artery of thigh
+
+Vastus medialis muscle
+
+Gracilis muscle
+
+Artery in adductor canal
+
+Rectus femoris muscle
+
+Vastus lateralis muscle
+
+
+Artery passes posteriorly through adductor hiatus and becomes popliteal artery
+
+Vastus medialis muscle
+
+Sartorius muscle
+
+
+■     posteriorly between the pectineus and adductor longus muscles and then between the adductor longus and adductor brevis muscles, and
+■     then travels inferiorly between the adductor longus and
+adductor magnus, eventually penetrating through the	Fig. 6.65  Femoral artery. adductor  magnus  to  connect  with  branches  of  the
+popliteal artery behind the knee.
+
+The deep artery of the thigh has lateral and medial cir-cumflex femoral branches and three perforating branches.
+
+
+
+
+
+592
+Regional Anatomy  •  Thigh	6
+
+
+Lateral circumflex femoral artery
+The lateral circumflex femoral artery normally origi-nates proximally from the lateral side of the deep artery of the thigh, but may arise directly from the femoral artery (Fig.  6.66).  It  passes  deep  to  the  sartorius  and  rectus femoris and divides into three terminal branches:
+
+
+■     One vessel (descending branch) descends deep to the rectus femoris, penetrates the vastus lateralis muscle, and connects with a branch of the popliteal artery near the knee.
+■     One  vessel  (transverse  branch)  passes  laterally  to pierce  the  vastus  lateralis  and  then  circles  around the proximal shaft of  the femur to anastomose with
+
+■     One vessel (ascending branch) ascends laterally deep to the tensor fasciae latae muscle and connects with a branch of the medial circumflex femoral artery to form a channel, which circles the neck of the femur and sup-plies the neck and head of the femur.
+
+branches from the medial femoral circumflex artery, the inferior gluteal artery, and the first perforating artery to form the cruciate anastomosis around the hip.
+
+
+
+
+Superior gluteal artery
+
+
+Psoas and iliacus muscles
+
+Sartorius muscle
+
+Deep artery of thigh
+
+Lateral circumflex femoral artery Ascending branch
+Descending branch
+Rectus femoris muscle
+Medial circumflex femoral artery
+Pectineus muscle Adductor longus muscle
+Adductor brevis muscle
+
+First, second, and third perforating arteries
+
+Gracilis muscle
+
+Terminal end of deep artery of thigh
+
+Vastus intermedius muscle
+
+Adductor magnus muscle
+
+Vastus lateralis muscle
+
+
+Inferior gluteal artery
+
+Piriformis muscle
+
+Lateral femoral circumflex artery
+
+
+Cruciate anastomoses
+
+
+Medial circumflex femoral artery
+
+First perforating artery
+
+
+Second perforating artery
+
+
+Third perforating artery
+
+Adductor magnus muscle
+
+Terminal end of deep artery of thigh
+
+Adductor hiatus
+
+
+Cut vastus medialis muscle
+
+Quadriceps femoris tendon
+
+Sartorius muscle
+
+Popliteal artery
+
+
+
+A	B
+
+Fig. 6.66  Deep artery of thigh. A. Anterior view. B. Posterior view.	593
+Lower Limb
+
+
+
+Medial circumflex femoral artery
+The medial circumflex femoral artery normally origi-nates proximally from the posteromedial aspect of the deep artery of  the thigh, but may originate from the femoral artery (Fig. 6.66). It passes medially around the shaft of the femur, first between the pectineus and iliopsoas and then between the obturator externus and adductor brevis muscles. Near the margin of the adductor brevis the vessel gives off a small branch, which enters the hip joint through the acetabular notch and anastomoses with the acetabular branch of the obturator artery.
+The main trunk of the medial circumflex femoral artery passes over the superior margin of the adductor magnus and divides into two major branches deep to the quadratus femoris muscle:
+
+
+Obturator artery
+The obturator artery originates as a branch of the inter-nal iliac artery in the pelvic cavity and enters the medial compartment of  the thigh through the obturator canal (Fig. 6.67). As it passes through the canal, it bifurcates into an anterior branch and a posterior branch, which together form a channel that circles the margin of  the obturator membrane and lies within the attachment of the obturator externus muscle.
+Vessels arising from the anterior and posterior branches supply adjacent muscles and anastomose with the inferior gluteal and medial circumflex femoral arteries. In addition, an acetabular vessel originates from the posterior branch, enters the hip joint through the acetabular notch, and
+
+
+■     One branch ascends to the trochanteric fossa and con-nects with branches of the gluteal and lateral circumflex femoral arteries.
+■     The other branch passes laterally to participate with branches from the lateral circumflex femoral artery, the inferior gluteal artery, and the first perforating artery in forming  an  anastomotic  network  of  vessels  around the hip.
+
+contributes to the supply of the head of the femur.
+
+
+Obturator artery
+
+
+
+
+
+Artery of ligament of head of femur
+
+
+
+Perforating arteries
+The three perforating arteries branch from the deep artery of the thigh (Fig. 6.66) as it descends anterior to the adductor  brevis  muscle—the  first  originates  above  the muscle, the second originates anterior to the muscle, and the third originates below the muscle. All three penetrate through the adductor magnus near its attachment to the linea aspera to enter and supply the posterior compart-ment of the thigh. Here, the vessels have ascending and descending branches, which interconnect to form a longi-tudinal channel, which participates above in forming an anastomotic network of vessels around the hip and inferi-orly anastomoses with branches of  the popliteal artery behind the knee.
+
+
+
+
+Ligament of head of femur
+
+
+
+
+
+Obturator externus muscle
+
+
+
+Fig. 6.67  Obturator artery.
+
+
+
+
+
+
+
+
+
+Anterior branch
+Posterior branch
+Acetabular branch
+
+
+
+
+
+
+
+
+
+
+
+
+
+594
+Regional Anatomy  •  Thigh	6
+
+
+
+In the clinic
+
+Peripheral vascular disease
+Peripheral vascular disease is often characterized by reduced blood flow to the legs. This disorder may be caused by stenoses (narrowing) and/or occlusions (blockages) in the lower aorta and the iliac, femoral, tibial, and fibular vessels. Patients typically have chronic leg ischemia and “acute on chronic” leg ischemia.
+Chronic leg ischemia
+Chronic leg ischemia is a disorder in which vessels have undergone atheromatous change, and often there is significant luminal narrowing (usually over 50%). Most patients with peripheral arterial disease have widespread arterial disease (including cardiovascular and cerebrovascular disease), which may be clinically asymptomatic. Some of these patients develop such severe ischemia that the viability of the limb is threatened (critical limb ischemia).
+The commonest symptom of chronic leg ischemia is intermittent claudication. Patients typically have a history of pain that develops in the calf muscles (usually associated with occlusions or narrowing in the femoral artery) or the buttocks (usually associated with occlusion or narrowing in the aorto-iliac segments). The pain experienced in these
+
+
+
+
+
+Veins
+Veins in the thigh consist of  superficial and deep veins. Deep veins generally follow the arteries and have similar names. Superficial veins are in the superficial fascia, inter-connect with deep veins, and do not generally accompany arteries. The largest of the superficial veins in the thigh is the great saphenous vein.
+
+Great saphenous vein
+The great saphenous vein originates from a venous arch on the dorsal aspect of  the foot and ascends along the medial side of the lower limb to the proximal thigh (see
+
+
+
+muscles is often cramplike and occurs with walking. The patient rests and is able to continue walking up to the same distance until the pain recurs and stops walking as before.
+Acute on chronic ischemia
+In some patients with chronic limb ischemia, an acute event blocks the vessels or reduces the blood supply to such a degree that the viability of the limb is threatened.
+Occasionally a leg may become acutely ischemic with no evidence of underlying atheromatous disease. In these instances a blood clot is likely to have embolized from the heart. Patients with mitral valve disease and atrial fibrillation are prone to embolic disease.
+Critical limb ischemia
+Critical limb ischemia occurs when the blood supply to the limb is so poor that the viability of the limb is severely threatened, and in this case many patients develop gangrene, ulceration, and severe rest pain in the foot. These patients require urgent treatment, which may be in the form of surgical reconstruction, radiological angioplasty, or even amputation.
+
+
+
+
+
+
+
+p. 560). Here it passes through the saphenous ring in deep fascia covering the anterior thigh to connect with the femoral vein in the femoral triangle (see p. 566).
+
+
+Nerves
+There are three major nerves in the thigh, each associated with one of the three compartments. The femoral nerve is associated with the anterior compartment of the thigh, the obturator nerve is associated with the medial compartment of the thigh, and the sciatic nerve is associated with the posterior compartment of the thigh.
+
+
+
+
+
+
+
+
+
+
+
+
+
+595
+Lower Limb
+
+
+
+
+Femoral nerve
+The  femoral  nerve  originates  from  the  lumbar  plexus (spinal cord segments L2–L4) on the posterior abdominal wall and enters the femoral triangle of the thigh by passing under the inguinal ligament (Fig. 6.68). In the femoral triangle the femoral nerve lies on the lateral side of  the
+
+Immediately after passing under the inguinal ligament, the  femoral  nerve  divides  into  anterior  and  posterior branches, which supply muscles of the anterior compart-ment of  the thigh and skin on the anterior and medial aspects of  the thigh and on the medial sides of  the leg and foot.
+Branches of the femoral nerve (Fig. 6.68) include:
+
+femoral artery and is outside the femoral sheath, which surrounds the vessels.
+Before entering the thigh, the femoral nerve supplies branches to the iliacus and pectineus muscles.
+
+
+
+Femoral nerve
+
+Nerves to iliacus
+
+
+■     anterior  cutaneous  branches,  which  penetrate  deep fascia to supply skin on the front of the thigh and knee;
+■     numerous motor nerves, which supply the quadriceps femoris muscles (rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis muscles) and the sar-torius muscle; and
+■     one long cutaneous nerve, the saphenous nerve, which supplies skin as far distally as the medial side of the foot.
+
+
+
+Nerve to pectineus
+
+Anterior branch
+
+Nerve to sartorius
+
+
+Posterior branch
+
+
+Pectineus muscle
+
+
+Anterior cutaneous branches
+
+Adductor longus muscle
+
+
+
+Adductor magnus muscle
+
+Gracilis muscle
+
+Saphenous nerve
+
+Vastus lateralis muscle
+Rectus femoris muscle
+
+
+The saphenous nerve accompanies the femoral artery through the adductor canal, but does not pass through the adductor hiatus with the femoral artery. Rather, the saphe-nous nerve penetrates directly through connective tissues near the end of the canal to appear between the sartorius and gracilis muscles on the medial side of the knee. Here the saphenous nerve penetrates deep fascia and continues down the medial side of the leg to the foot, and supplies skin on the medial side of the knee, leg, and foot.
+
+Obturator nerve
+The obturator nerve is a branch of  the lumbar plexus (spinal cord segments L2–L4) on the posterior abdominal wall. It descends in the psoas muscle, and then passes out of the medial margin of the psoas muscle to enter the pelvis (Fig. 6.69). The obturator nerve continues along the lateral pelvic wall and then enters the medial compartment of the thigh by passing through the obturator canal. It supplies most of the adductor muscles and skin on the medial aspect of the thigh. As the obturator nerve enters the thigh, it divides into two branches, an anterior branch and a poste-rior branch, which are separated by the adductor brevis muscle:
+
+
+
+Vastus medialis muscle
+
+Sartorius muscle
+
+
+
+
+Pes anserinus Saphenous nerve
+
+
+596	Fig. 6.68  Femoral nerve.
+
+
+■     The posterior branch descends behind the adductor brevis muscle and on the anterior surface of the adduc-tor magnus muscle, and supplies the obturator externus and adductor brevis muscles and the part of the adduc-tor magnus that attaches to the linea aspera.
+■     The anterior branch descends on the anterior surface of the adductor brevis muscle and is behind the pectin-eus and adductor longus muscles—it supplies branches to the adductor longus, gracilis, and adductor brevis muscles, and often contributes to the supply of  the pectineus muscle, and cutaneous branches innervate the skin on the medial side of the thigh.
+Regional Anatomy  •  Thigh	6
+
+
+
+
+
+
+Psoas and iliacus muscles
+
+
+Obturator nerve
+
+
+Obturator externus muscle
+
+Posterior branch
+Anterior branch
+Pectineus muscle
+
+Adductor brevis muscle
+Cutaneous branch
+
+Adductor longus muscle
+
+Branch to adductor magnus from posterior branch
+
+Gracilis muscle
+
+Adductor magnus muscle
+
+
+Piriformis muscle
+
+
+Quadratus femoris muscle
+Branch to part of adductor magnus originating
+from ischial tuberosity
+Adductor magnus muscle
+
+Long head of biceps femoris muscle
+
+Sciatic nerve
+
+
+Short head of biceps femoris muscle
+Semitendinosus muscle
+Semimembranosus muscle
+
+
+
+Long head of biceps femoris muscle
+
+Tibial nerve
+Common fibular nerve
+Popliteal artery and vein
+
+
+
+
+
+
+Fig. 6.69  Obturator nerve.
+
+
+
+
+
+Sciatic nerve
+The sciatic nerve is a branch of  the lumbosacral plexus (spinal  cord  segments  L4–S3)  and  descends  into  the posterior compartment of the thigh from the gluteal region (Fig. 6.70). It innervates all muscles in the posterior com-partment of the thigh and then its branches continue into the leg and foot.
+In the posterior compartment of the thigh, the sciatic nerve lies on the adductor magnus muscle and is crossed by the long head of the biceps femoris muscle.
+Proximal  to  the  knee,  and  sometimes  within  the pelvis,  the  sciatic  nerve  divides  into  its  two  terminal branches: the tibial  nerve and the common  fibular nerve. These nerves travel vertically down the thigh and
+
+Fig. 6.70  Sciatic nerve.
+
+
+
+enter the popliteal fossa posterior to the knee. Here, they meet the popliteal artery and vein.
+
+Tibial nerve
+The tibial part of the sciatic nerve, either before or after its separation  from  the  common  fibular  nerve,  supplies branches to all muscles in the posterior compartment of the thigh (long head of biceps femoris, semimembranosus, semitendinosus)  except  the  short  head  of   the  biceps
+femoris, which is innervated by the common fibular part	597 (Fig. 6.70).
+Lower Limb
+
+
+
+The tibial nerve descends through the popliteal fossa, enters the posterior compartment of the leg, and continues into the sole of the foot.
+The tibial nerve innervates:
+
+
+
+
+Posterior cruciate ligament
+
+
+Intercondylar fossa
+
+Anterior cruciate ligament
+
+
+
+■     all muscles in the posterior compartment of the leg,
+■     all intrinsic muscles in the sole of the foot including the first  two  dorsal  interossei  muscles,  which  also  may receive innervation from the deep fibular nerve, and
+■     skin on the posterolateral side of the lower half of the leg and lateral side of the ankle, foot, and little toe, and
+skin on the sole of the foot and toes.	Patella
+
+
+Fibular collateral ligament
+
+
+
+
+Common fibular nerve
+The common fibular part of the sciatic nerve innervates the short head of the biceps femoris in the posterior com-partment of the thigh and then continues into the lateral and anterior compartments of the leg and onto the foot (Fig. 6.70).
+
+
+
+Patellar ligament
+
+
+
+
+
+Tendon of popliteus muscle
+
+
+
+The common fibular nerve innervates:
+Infrapatellar fat
+■     all muscles in the anterior and lateral compartments of the leg,
+■     one muscle (extensor digitorum brevis) on the dorsal aspect of the foot,
+■     the first two dorsal interossei muscles in the sole of the
+
+
+Lateral meniscus
+
+
+
+
+Proximal tibiofibular joint
+
+
+
+foot, and
+■     skin over the lateral aspect of the leg, and ankle, and over the dorsal aspect of the foot and toes.
+
+
+Fig. 6.71  Knee joint. Joint capsule is not shown.
+
+
+flexion and extension. Like all hinge joints, the knee joint
+
+
+
+
+Knee joint
+The knee joint is the largest synovial joint in the body. It consists of:
+
+is reinforced by collateral ligaments, one on each side of the joint. In addition, two very strong ligaments (the cruci-ate ligaments) interconnect the adjacent ends of the femur and tibia and maintain their opposed positions during
+
+
+
+
+■     the articulation between the femur and tibia, which is weight-bearing, and
+■     the articulation between the patella and the femur, which allows the pull of the quadriceps femoris muscle to  be  directed  anteriorly  over  the  knee  to  the  tibia without tendon wear (Fig. 6.71).
+
+Two  fibrocartilaginous  menisci,  one  on  each  side,
+
+movement.
+Because the knee joint is involved in weight-bearing, it has an efficient “locking” mechanism to reduce the amount of muscle energy required to keep the joint extended when standing.
+
+Articular surfaces
+The articular surfaces of the bones that contribute to the knee joint are covered by hyaline cartilage. The major
+
+between  the  femoral  condyles  and  tibia  accommodate	surfaces involved include: changes in the shape of the articular surfaces during joint
+
+movements.
+The detailed movements of the knee joint are complex, but basically the joint is a hinge joint that allows mainly
+
+■     the two femoral condyles, and
+■     the adjacent surfaces of the superior aspect of the tibial condyles.
+
+
+
+598
+Regional Anatomy  •  Thigh	6
+
+
+
+The surfaces of  the femoral condyles that articulate with the tibia in flexion of the knee are curved or round, whereas the surfaces that articulate in full extension are flat (Fig. 6.72).
+The articular surfaces between the femur and patella are the V-shaped trench on the anterior surface of  the distal end of the femur where the two condyles join and the adjacent surfaces on the posterior aspect of the patella. The joint surfaces are all enclosed within a single articular cavity,  as  are  the  intraarticular  menisci  between  the femoral and tibial condyles.
+
+
+Menisci
+There  are  two  menisci,  which  are  fibrocartilaginous C-shaped cartilages, in the knee joint, one medial (medial meniscus) and the other lateral (lateral meniscus) (Fig. 6.73). Both are attached at each end to facets in the inter-condylar region of the tibial plateau.
+The medial meniscus is attached around its margin to the capsule of the joint and to the tibial collateral ligament, whereas the lateral meniscus is unattached to the capsule. Therefore, the lateral meniscus is more mobile than the medial meniscus.
+The menisci are interconnected anteriorly by a trans-verse ligament of  the knee. The lateral meniscus is also connected to the tendon of  the popliteus muscle, which
+
+
+
+Femur
+
+
+Patella
+
+Meniscus
+
+Tibia
+
+Flat	Round	passes  superolaterally  between  this  meniscus  and  the capsule to insert on the femur.
+The menisci improve congruency between the femoral and tibial condyles during joint movements where the surfaces of the femoral condyles articulating with the tibial plateau change from small curved surfaces in flexion to large flat surfaces in extension.
+
+
+
+A
+
+Intercondylar region
+
+
+
+
+
+Posterior cruciate ligament
+Meniscus
+
+B
+
+Patella
+Surface for articulation
+with patella	Infrapatellar fat
+Flat surfaces for articulation with tibia in extension
+
+
+
+
+Transverse ligament of the knee
+
+Patellar ligament
+Joint capsule
+
+
+
+
+
+
+Anterior cruciate ligament
+
+Round surfaces for articulation with tibia in flexion
+
+
+
+
+C	 Popliteus tendon	Lateral meniscus	Medial meniscus A
+
+Fig. 6.72  Articular surfaces of the knee joint. A. Extended. B. Flexed. C. Anterior view (flexed).
+
+
+Fig. 6.73  Menisci of the knee joint. A. Superior view.
+
+Continues
+
+
+
+
+
+
+599
+Lower Limb
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Medial femoral condyle	Lateral femoral condyle
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+B
+
+Anterior
+
+
+Tibia
+Normal medial meniscus
+
+C
+
+Anterior
+
+
+Tibia	Fibula
+Normal lateral meniscus
+
+
+Fig. 6.73, cont’d  Menisci of the knee joint. B. Normal knee joint showing the medial meniscus. T2-weighted magnetic resonance image in the sagittal plane. C. Normal knee joint showing the lateral meniscus. T2-weighted magnetic resonance image in the sagittal plane.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+600
+Regional Anatomy  •  Thigh	6
+
+
+
+In the clinic
+
+Meniscal injuries
+Menisci can get torn during forceful rotation or twisting of the knee, but significant trauma is not always necessary for a tear to occur. There are various patterns of meniscal tearing depending on the cleavage plane such as vertical tears (perpendicular to the tibial plateau), horizontal tears (parallel to the long axis of the meniscus and perpendicular to the tibial plateau), or bucket handle tears (longitudinal tear where the torn portion of the meniscus forms a handle shaped fragment which gets displaced into the intercondylar notch).
+
+
+
+The patient usually complains of pain localized to the medial or lateral side of the knee, knee locking or clicking, sensation of knee giving way, and swelling, which can be intermittent and usually delayed.
+MRI is the modality of choice to assess meniscal tears and detect other associated injuries, such as ligamentous tears and articular cartilage damage (Fig. 6.74A). Arthroscopy is usually performed to repair a tear, debride the damaged meniscal material, or rarely remove the entire torn meniscus (Fig. 6.74B).
+
+
+
+Medial meniscus tear
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+A	B
+
+Fig. 6.74  Meniscal injury and repair. A. Sagittal MRI of a knee joint showing tear of the medial meniscus. B. Coronal MRI of a knee showing a truncated lateral meniscus after partial meniscectomy to treat a tear.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+601
+Lower Limb
+
+
+
+
+Synovial membrane
+The synovial membrane of the knee joint attaches to the margins of the articular surfaces and to the superior and inferior outer margins of the menisci (Fig. 6.75A). The two
+
+synovial fold), which attaches to the margin of the inter-condylar fossa of the femur.
+The synovial membrane of the knee joint forms pouches in two locations to provide low-friction surfaces for the movement of tendons associated with the joint:
+
+cruciate  ligaments,  which  attach  in  the  intercondylar region of the tibia below and the intercondylar fossa of the femur above, are outside the articular cavity, but enclosed within the fibrous membrane of the knee joint.
+Posteriorly,  the  synovial  membrane  reflects  off  the fibrous membrane of  the joint capsule on either side of the posterior cruciate ligament and loops forward around both ligaments thereby excluding them from the articular cavity.
+Anteriorly, the synovial membrane is separated from the patellar ligament by an infrapatellar fat pad. On each side of  the pad, the synovial membrane forms a fringed margin (an alar fold), which projects into the articular cavity.  In  addition,  the  synovial  membrane  covering the lower part of the infrapatellar fat pad is raised into a
+
+
+■     The smallest of these expansions is the subpopliteal recess  (Fig.  6.75A),  which  extends  posterolaterally from the articular cavity and lies between the lateral meniscus and the tendon of the popliteus muscle, which passes through the joint capsule.
+■     The second expansion is the suprapatellar bursa (Fig. 6.75B), a large bursa that is a continuation of  the articular cavity superiorly between the distal end of the shaft of the femur and the quadriceps femoris muscle and tendon—the apex of this bursa is attached to the small articularis genus muscle, which pulls the bursa away from the joint during extension of the knee.
+
+Other bursae associated with the knee but not normally
+
+sharp midline fold directed posteriorly (the infrapatellar	communicating  with  the  articular  cavity  include  the
+
+
+
+
+
+Posterior cruciate ligament	Anterior cruciate ligament
+
+
+Infrapatellar fold                                                 Alar fold                Quadriceps femoris tendon
+
+Synovial membrane
+
+
+
+Articularis genus
+
+
+
+Infrapatellar fat
+
+
+Patellar ligament
+
+
+Popliteus tendon
+Patella
+
+
+Prepatellar bursa
+
+
+Suprapatellar bursa
+
+
+
+Subpopliteal recess
+
+
+Patellar ligament
+
+
+
+Tibia	Lateral meniscus
+
+
+Infrapatellar fat
+
+
+
+
+Fibula
+
+
+A
+
+Subcutaneous and deep infrapatellar bursae
+
+Anterior	Posterior
+
+B
+
+
+Fig. 6.75  Synovial membrane of the knee joint and associated bursae. A. Superolateral view; patella and femur not shown. B. Paramedial 602	sagittal section through the knee.
+Regional Anatomy  •  Thigh	6
+
+
+
+subcutaneous prepatellar bursa, deep and subcutaneous infrapatellar bursae, and numerous other bursae associ-
+
+■     Anteriorly, the fibrous membrane is attached to the margins of the patella where it is reinforced with tendi-
+
+ated  with  tendons  and  ligaments  around  the  joint	nous expansions from the vastus lateralis and vastus
+
+(Fig. 6.75B).
+The  prepatellar  bursa  is  subcutaneous  and  anterior to the patella. The deep and subcutaneous infrapatellar bursae are on the deep and subcutaneous sides of  the patellar ligament, respectively.
+
+Fibrous membrane
+The fibrous membrane of the knee joint is extensive and is partly formed and reinforced by extensions from tendons of  the surrounding muscles (Fig. 6.76). In general, the fibrous membrane encloses the articular cavity and the intercondylar region:
+
+medialis muscles, which also merge above with the quadriceps femoris tendon and below with the patellar ligament.
+
+The fibrous membrane is reinforced anterolaterally by a fibrous extension from the iliotibial tract and posteromedi-ally by an extension from the tendon of the semimembra-nosus (the oblique popliteal ligament), which reflects superiorly across the back of the fibrous membrane from medial to lateral.
+The upper end of the popliteus muscle passes through an aperture in the posterolateral aspect of  the fibrous membrane of  the knee and is enclosed by the fibrous
+
+■     On  the  medial  side  of  the  knee  joint,  the  fibrous	membrane as its tendon travels around the joint to insert
+
+membrane blends with the tibial collateral ligament and is attached on its internal surface to the medial meniscus.
+■     Laterally, the external surface of the fibrous membrane is separated by a space from the fibular collateral liga-ment and the internal surface of the fibrous membrane is not attached to the lateral meniscus.
+
+on the lateral aspect of the lateral femoral condyle.
+
+Ligaments
+The major ligaments associated with the knee joint are the patellar ligament, the tibial (medial) and fibular (lateral) collateral ligaments, and the anterior and posterior cruci-ate ligaments.
+
+
+
+
+
+
+
+
+
+
+
+Vastus lateralis muscle
+
+
+Iliotibial tract
+
+
+Fibular collateral ligament
+
+Patellar ligament
+
+Vastus medialis muscle
+
+Quadriceps femoris tendon
+
+
+Tibial collateral ligament
+
+Semitendinosus
+
+Gracilis
+
+Sartorius
+
+
+
+
+Semimembranosus tendon
+
+
+Oblique popliteal ligament
+
+
+
+
+Popliteus muscle
+
+
+
+
+
+
+
+A	B
+
+Fig. 6.76  Fibrous membrane of the knee joint capsule. A. Anterior view. B. Posterior view.	603
+Lower Limb
+
+
+
+
+Patellar ligament
+The patellar ligament is basically the continuation of the  quadriceps  femoris  tendon  inferior  to  the  patella (Fig. 6.76). It is attached above to the margins and apex of the patella and below to the tibial tuberosity.
+
+Collateral ligaments
+The collateral ligaments, one on each side of  the joint, stabilize the hinge-like motion of the knee (Fig. 6.77).
+
+
+
+
+
+
+
+Fibular collateral ligament
+
+The cord-like fibular collateral ligament is attached superiorly to the lateral femoral epicondyle just above the groove for the popliteus tendon. Inferiorly, it is attached to a depression on the lateral surface of the fibular head. It is separated from the fibrous membrane by a bursa.
+The  broad  and  flat  tibial  collateral  ligament  is attached by much of  its deep surface to the underlying fibrous membrane. It is anchored superiorly to the medial femoral epicondyle just inferior to the adductor tubercle and descends anteriorly to attach to the medial margin and
+
+
+
+
+
+
+Tibial collateral ligament
+
+
+
+
+
+
+Tendon of popliteus muscle
+
+Biceps femoris
+
+Iliotibial tract
+Attaches to medial meniscus
+
+Patellar ligament
+
+
+
+
+
+Attaches to capsule
+
+
+Gracilis
+Sartorius	Semitendinosus
+
+
+
+
+A
+
+Lateral femoral condyle
+
+B
+Patella	Posterior cruciate ligament
+Medial femoral condyle
+
+
+
+Lateral femoral condyle
+
+
+
+
+
+
+
+
+
+Fibular collateral ligament
+
+Tibial collateral ligament
+
+
+
+
+C	D
+
+
+Fibula	Tibia	Patellar ligament	Medial meniscus
+Anterior cruciate ligament
+
+Lateral meniscus Tibia
+
+
+Fig. 6.77  Collateral ligaments of the knee joint. A. Lateral view. B. Medial view. C. Normal knee joint showing the patellar ligament and the fibular collateral ligament. T1-weighted magnetic resonance image in the sagittal plane. D. Normal knee joint showing the tibial collateral ligament, the medial and lateral menisci, and the anterior and posterior cruciate ligaments. T1-weighted magnetic resonance image in the
+604	coronal plane.
+Regional Anatomy  •  Thigh	6
+
+
+medial surface of the tibia above and behind the attach-	The   anterior   cruciate   ligament   prevents   anterior
+
+ment of the sartorius, gracilis, and semitendinosus tendons.
+
+Cruciate ligaments
+The  two  cruciate  ligaments  are  in  the  intercondylar region of the knee and interconnect the femur and tibia (Figs. 6.77D and 6.78). They are termed “cruciate” (Latin for “shaped like a cross”) because they cross each other in  the  sagittal  plane  between  their  femoral  and  tibial attachments:
+
+displacement of  the tibia relative to the femur and the posterior cruciate ligament restricts posterior displacement (Fig. 6.78).
+
+Locking mechanism
+When standing, the knee joint is locked into position, thereby reducing the amount of muscle work needed to maintain the standing position (Fig. 6.79).
+One component of the locking mechanism is a change
+
+
+
+
+■     The anterior cruciate ligament attaches to a facet on the anterior part of  the intercondylar area of  the
+
+in the shape and size of the femoral surfaces that articulate with the tibia:
+
+
+
+tibia and ascends posteriorly to attach to a facet at the back of the lateral wall of the intercondylar fossa of the femur.
+■     The  posterior  cruciate  ligament  attaches  to  the posterior aspect of the intercondylar area of the tibia and ascends anteriorly to attach to the medial wall of the intercondylar fossa of the femur.
+
+■     In flexion, the surfaces are the curved and rounded areas on the posterior aspects of the femoral condyles.
+
+
+The anterior cruciate ligament crosses lateral to the posterior cruciate ligament as they pass through the inter-
+
+condylar region.
+
+Intercondylar fossa
+
+
+
+Posterior cruciate ligament
+
+
+
+
+
+Anterior cruciate ligament
+
+
+
+Posterior displacement of tibia on fixed femur restricted by posterior cruciate ligament
+
+
+
+
+
+
+Posterior
+
+
+
+
+
+
+
+Flat surface of femoral condyles is in contact with tibia and stabilizes joint
+
+
+Medial rotation of femur on tibia tightens ligaments
+
+
+
+
+
+
+Anterior
+
+
+
+
+
+
+
+Anterior displacement of tibia on fixed femur restricted by anterior cruciate ligament
+
+
+Line of center of gravity is anterior to knee joint and maintains extension
+
+
+Fig. 6.78  Cruciate ligaments of the knee joint. Superolateral view.	Fig. 6.79  Knee “locking” mechanism.	605
+Lower Limb
+
+
+
+■     As the knee is extended, the surfaces move to the broad and flat areas on the inferior aspects of  the femoral condyles.
+
+Consequently the joint surfaces become larger and more
+
+
+Descending branch of lateral circumflex femoral artery
+
+
+Femoral artery
+
+
+
+Adductor magnus
+
+
+
+stable in extension.
+Another component of the locking mechanism is medial rotation of the femur on the tibia during extension. Medial rotation  and  full  extension  tightens  all  the  associated ligaments.
+Another feature that keeps the knee extended when standing is that the body’s center of gravity is positioned along a vertical line that passes anterior to the knee joint. The popliteus muscle unlocks the knee by initiating
+lateral rotation of the femur on the tibia.
+
+Vascular supply and innervation
+Vascular supply to the knee joint is predominantly through descending and genicular branches from the femoral, pop-liteal, and lateral circumflex femoral arteries in the thigh and the circumflex fibular artery and recurrent branches from the anterior tibial artery in the leg. These vessels form an anastomotic network around the joint (Fig. 6.80).
+The  knee  joint  is  innervated  by  branches  from  the obturator, femoral, tibial, and common fibular nerves.
+
+
+
+
+
+
+
+
+
+
+
+Superior lateral genicular artery
+
+
+
+Inferior lateral genicular artery
+
+
+
+Circumflex fibular artery
+
+
+Adductor hiatus
+
+Descending genicular artery
+
+
+Saphenous branch
+
+Superior medial genicular artery
+
+
+
+Popliteal artery
+
+
+
+
+Inferior medial genicular artery
+
+
+
+
+In the clinic
+
+Collateral ligament injuries
+The collateral ligaments are responsible for stabilizing the knee joint, controlling its sideway movements, and protecting the knee from excessive motion.
+Injury to the fibular collateral ligament occurs when excessive outward force is applied to the medial side of the knee (varus force), and is less common than an injury to the tibial collateral ligament that is damaged when excessive force is applied inward to the lateral side of the joint (valgus force). Injuries to the tibial collateral ligament can be part of a so called “unhappy triad” that also involves tears of the medial meniscus and the anterior cruciate ligament.
+The spectrum of injuries to collateral ligaments of the knee range from minor sprains where the ligaments are slightly stretched, but still able to stabilize the knee joint, to full thickness tears where all fibers are torn and the ligaments lose their stabilizing function.
+
+Recurrent branch
+of anterior tibial	Posterior
+tibial artery
+Interosseous membrane
+Anterior tibial artery
+
+
+Fig. 6.80  Anastomoses of arteries around the knee. Anterior view.
+
+
+
+
+
+
+
+
+606
+Regional Anatomy  •  Thigh	6
+
+
+
+In the clinic
+
+Cruciate ligament injuries
+The anterior cruciate ligament (ACL) is most frequently injured during non-contact activities when there is a sudden change in the direction of movement (cutting or pivoting) (Fig. 6.81). Contact sports may also result in ACL injury due to sudden twisting, hyperextension, and valgus force related to direct collision. The injury usually affects the mid-portion of the ligament and manifests itself as a complete or partial discontinuity of the fibers or abnormal orientation and contour of the ligament. With an acute ACL tear, a sudden click or pop can be heard and the knee becomes rapidly swollen. Several tests are used to clinically assess the injury, and the diagnosis is usually confirmed by MRI. A full thickness ACL tear causes instability of the knee joint. The treatment depends on the desired level of activity of the patient. In those with high activity levels, surgical reconstruction of the ligament is required. Those with low activity levels may opt for knee bracing and physiotherapy; however, in the long term the internal damage to the knee leads to the development of early osteoarthritis.
+A tear to the posterior cruciate ligament (PCL) requires significant force, so it rarely occurs in isolation. It usually occurs during hyperextension of the knee or as a result of a direct blow to a bent knee such as when striking the knee against the dashboard in a motor vehicle accident. Typically, the injury presents as posterior displacement of the tibia on physical examination (the so called tibial sag sign). Patients complain of knee pain and swelling, inability to bear weight,
+
+
+
+In the clinic
+
+Degenerative joint disease/osteoarthritis Degenerative joint disease occurs throughout many joints
+within the body. Articular degeneration may result from an abnormal force across the joint with a normal cartilage or a normal force with abnormal cartilage.
+Typically degenerative joint disease occurs in synovial joints and the process is called osteoarthritis. In the joints where osteoarthritis occurs the cartilage and bony tissues are usually involved, with limited change within the synovial membrane. The typical findings include reduction in the joint space, eburnation (joint sclerosis), osteophytosis (small bony outgrowths), and bony cyst formation. As the disease progresses the joint may become malaligned, its movement may become severely limited, and there may be significant pain.
+The commonest sites for osteoarthritis include the small joints of the hands and wrist, and in the lower limb, the hip and knee are typically affected, though the tarsometatarsal and metatarsophalangeal articulations may undergo similar changes.
+The etiology of degenerative joint disease is unclear, but there are some associations, including genetic
+
+
+
+and instability. The diagnosis is confirmed on MRI. The management, as in ACL injury, depends on the degree of the injury (sprain, partial thickness, full thickness) and the level of desired activity.
+
+
+ACL rupture
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Fig. 6.81  Sagittal MRI of knee joint showing rupture of the anterior cruciate ligament.
+
+
+
+
+
+predisposition, increasing age (males tend to be affected younger than females), overuse or underuse of joints, and nutritional and metabolic abnormalities. Further factors include joint trauma and pre-existing articular disease or deformity.
+The histological findings of osteoarthritis consist of degenerative changes within the cartilage and the subchondral bone. Further articular damage worsens these changes, which promote further abnormal stresses upon the joint. As the disease progresses the typical finding is pain, which is usually worse on rising from bed and at the end of a day’s activity. Commonly it is aggravated by the extremes of movement or unaccustomed exertion. Stiffness and limitation of movement may ensue.
+Treatment in the first instance includes alteration of lifestyle to prevent pain and simple analgesia. As symptoms progress a joint replacement may be necessary, but although joint replacement appears to be the panacea for degenerative joint disease, it is not without risks and complications, which include infection and failure in the
+short and long term.	607
+Lower Limb
+
+
+
+In the clinic
+
+Examination of the knee joint
+It is important to establish the nature of the patient’s complaint before any examination. The history should include information about the complaint, the signs and symptoms, and the patient’s lifestyle (level of activity). This history may give a significant clue to the type of injury and the likely findings on clinical examination, for example, if the patient was kicked around the medial aspect of the knee, a valgus deformity injury to the tibial collateral ligament might be suspected.
+The examination should include assessment in the erect position, while walking, and on the couch. The affected side must be compared with the unaffected side.
+There are many tests and techniques for examining the knee joint, including the following.
+Tests for anterior instability
+■     Lachman’s test—the patient lies on the couch. The examiner places one hand around the distal femur and the other around the proximal tibia and then elevates the knee, producing 20° of flexion. The patient’s heel rests on the couch. The examiner’s thumb must be on the tibial tuberosity. The hand on the tibia applies a brisk anteriorly directed force. If the movement of the tibia on the femur comes to a sudden stop, it is a firm endpoint. If it does not come to a sudden stop, the endpoint is described as soft and is associated with a tear of the anterior cruciate ligament.
+■     Anterior drawer test—a positive anterior drawer test is when the proximal head of a patient’s tibia can be pulled anteriorly on the femur. The patient lies supine on the couch. The knee is flexed to 90° and the heel and sole of the foot are placed on the couch. The examiner sits gently on the patient’s foot, which has been placed in a neutral position. The index fingers are used to check that the hamstrings are relaxed while the other fingers encircle the upper end of the tibia and pull the tibia. If the tibia moves forward, the anterior cruciate ligament is torn. Other peripheral structures, such as the medial meniscus or meniscotibial ligaments, must also be damaged to elicit this sign.
+■     Pivot shift test—there are many variations of this test. The patient’s foot is wedged between the examiner’s body and elbow. The examiner places one hand flat under the tibia pushing it forward with the knee in extension. The other hand is placed against the patient’s thigh pushing it the other way. The lower limb is taken
+
+
+
+into slight abduction by the examiner’s elbow with the examiner’s body acting as a fulcrum to produce the valgus. The examiner maintains the anterior tibial translation and the valgus and initiates flexion of the patient’s knee. At about 20°–30° the pivot shift will occur as the lateral tibial plateau reduces. This test demonstrates damage to the posterolateral corner of the knee joint and the anterior cruciate ligament.
+
+Tests for posterior instability
+■     Posterior drawer test—a positive posterior drawer test occurs when the proximal head of a patient’s tibia can be pushed posteriorly on the femur. The patient is placed in a supine position and the knee is flexed to approximately 90° with the foot in the neutral position. The examiner sits gently on the patient’s foot placing both thumbs on the tibial tuberosity and pushing the tibia backward. If the tibial plateau moves, the posterior cruciate ligament is torn.
+
+Assessment of other structures of the knee
+■     Assessment of the tibial collateral ligament can be performed by placing a valgus stress on the knee.
+■     Assessment of lateral and posterolateral knee structures requires more complex clinical testing.
+
+The knee will also be assessed for:
+
+■     joint line tenderness,
+■     patellofemoral movement and instability, ■     presence of an effusion,
+■     muscle injury, and
+■     popliteal fossa masses.
+Further investigations
+After the clinical examination has been carried out, further investigations usually include plain radiography and possibly magnetic resonance imaging, which allows the radiologist to assess the menisci, cruciate ligaments, collateral ligaments, bony and cartilaginous surfaces, and soft tissues.
+Arthroscopy may be carried out and damage to any internal structures repaired or trimmed. An arthroscope is a small camera that is placed into the knee joint through the anterolateral or anteromedial aspect of the knee joint. The joint is filled with a saline solution and the telescope is manipulated around the knee joint to assess the cruciate ligaments, menisci, and cartilaginous surfaces.
+
+
+
+
+
+
+
+
+608
+Regional Anatomy  •  Thigh	6
+
+
+
+In the clinic
+
+Anterolateral ligament of the knee
+A ligament associated at its origin with the fibular collateral ligament of the knee has been described. This ligament (anterolateral ligament of the knee) courses from the lateral femoral epicondyle to the anterolateral region of the proximal end of the tibia and may control internal rotation of the tibia. (J Anat 2013;223:321–328)
+
+
+
+
+
+
+
+
+
+
+
+
+
+Tibiofibular joint
+The small proximal tibiofibular joint is synovial in type and allows very little movement (Fig. 6.82). The opposing joint surfaces, on the undersurface of the lateral condyle of the tibia and on the superomedial surface of the head of the fibula, are flat and circular. The capsule is reinforced by anterior and posterior ligaments.
+
+
+Popliteal fossa
+The popliteal fossa is an important area of  transition between the thigh and leg and is the major route by which structures pass from one region to the other.
+The popliteal fossa is a diamond-shaped space behind the knee joint formed between muscles in the posterior compartments of the thigh and leg (Fig. 6.83A):
+
+
+
+
+
+
+
+
+
+Anterolateral ligament
+of knee
+Iliotibial tract Fibular
+collateral ligament
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Fibular collateral ligament
+
+
+
+
+Proximal tibiofibular joint
+
+
+Anterior ligament of joint
+
+
+
+■     The margins of  the upper part of  the diamond are formed medially by the distal ends of the semitendinosus and semimembranosus muscles and laterally by the distal end of the biceps femoris muscle.
+■     The margins of the smaller lower part of the space are formed medially by the medial head of the gastrocne-mius muscle and laterally by the plantaris muscle and the lateral head of the gastrocnemius muscle.
+■     The floor of the fossa is formed by the capsule of the knee joint and adjacent surfaces of the femur and tibia, and, more inferiorly, by the popliteus muscle.
+■     The roof is formed by deep fascia, which is continuous above with the fascia lata of the thigh and below with deep fascia of the leg.
+
+
+Interosseous membrane
+
+
+Fig. 6.82  Tibiofibular joint.
+
+
+
+
+
+
+
+
+
+609
+Lower Limb
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Biceps femoris muscle (short head)
+
+Vein
+Artery	Nerve
+
+
+
+Semimembranosus muscle
+
+Adductor magnus muscle
+
+Linea aspera
+
+
+Femoral vein
+
+Femoral artery
+
+
+Medial	Lateral
+
+Sciatic nerve
+
+
+
+
+
+Biceps femoris muscle
+(long head)
+
+Posterior cutaneous nerve of thigh
+
+
+Adductor hiatus
+
+
+Semitendinosus muscle
+
+
+
+
+Medial head of gastrocnemius muscle
+
+
+
+Popliteus muscle
+
+A
+
+
+Popliteal fossa
+Plantaris muscle
+
+
+Lateral head of gastrocnemius muscle
+
+Small saphenous vein
+
+
+B
+
+
+Tibial nerve Popliteal vein Popliteal artery
+
+Common fibular nerve
+
+
+
+
+
+
+
+
+C
+
+
+
+
+Posterior cutaneous nerve of thigh
+
+
+
+Small saphenous vein
+
+
+Fig. 6.83  Popliteal fossa. A. Boundaries. B. Nerves and vessels. C. Superficial structures.
+
+
+
+
+
+
+
+
+
+
+610
+Regional Anatomy  •  Thigh	6
+
+
+
+
+Contents
+The major contents of the popliteal fossa are the popliteal artery, the popliteal vein, and the tibial and common fibular nerves (Fig. 6.83B).
+
+Tibial and common fibular nerves
+The tibial and common fibular nerves originate proximal to the popliteal fossa as the two major branches of  the sciatic nerve. They are the most superficial of the neuro-vascular structures in the popliteal fossa and enter the region directly from above under the margin of the biceps femoris muscle:
+
+of  the leg where it ends just lateral to the midline of the leg by dividing into the anterior and posterior tibial arteries.
+The popliteal artery is the deepest of the neurovascular structures in the popliteal fossa and is therefore difficult to palpate; however, a pulse can usually be detected by deep palpation near the midline.
+In the popliteal fossa, the popliteal artery gives rise to branches, which supply adjacent muscles, and to a series of geniculate arteries, which contribute to vascular anas-tomoses around the knee.
+The popliteal vein is superficial to and travels with the popliteal artery. It exits the popliteal fossa superiorly to
+
+
+
+
+■     The tibial nerve descends vertically through the popli-teal fossa and exits deep to the margin of the plantaris muscle to enter the posterior compartment of the leg.
+■     The  common  fibular  nerve  exits  by  following  the biceps femoris tendon over the lower lateral margin of  the popliteal fossa, and continues to the lateral side of  the leg where it swings around the neck of the  fibula  and  enters  the  lateral  compartment  of the leg.
+
+become the femoral vein by passing through the adductor hiatus.
+
+Roof of popliteal fossa
+The roof  of  the popliteal fossa is covered by superficial fascia and skin (Fig. 6.83C). The most important struc-ture  in  the  superficial  fascia  is  the  small  saphenous vein.  This  vessel  ascends  vertically  in  the  superficial fascia on the back of the leg from the lateral side of the dorsal venous arch in the foot. It ascends to the back
+
+
+
+
+Popliteal artery and vein
+The popliteal artery is the continuation of  the femoral artery in the anterior compartment of  the thigh, and begins as the femoral artery passes posteriorly through the adductor hiatus in the adductor magnus muscle.
+The popliteal artery appears in the popliteal fossa on the upper medial side under the margin of the semimem-branosus muscle. It descends obliquely through the fossa with the tibial nerve and enters the posterior compartment
+
+
+
+
+
+In the clinic
+
+Popliteal artery aneurysm
+The popliteal artery can become abnormally dilated, forming an aneurysm. The artery is considered aneurysmal when its diameter exceeds 7 mm. Although popliteal artery aneurysms can occur in isolation, they are most commonly associated with aneurysms in other large vessels such as the femoral artery or the thoracic or abdominal aorta. Therefore, once a popliteal aneurysm has been detected, the entire arterial tree needs to be investigated for the presence of coexisting aneurysms elsewhere in the body.
+Popliteal artery aneurysms tend to undergo thrombosis and are less likely to rupture than other aneurysms.
+
+of  the  knee  where  it  penetrates  deep  fascia,  which forms the roof  of  the popliteal fossa, and joins with the popliteal vein.
+One other structure that passes through the roof of the fossa is the posterior cutaneous nerve of the thigh, which descends through the thigh superficial to the hamstring muscles, passes through the roof  of  the popliteal fossa, and then continues inferiorly with the small saphenous vein to innervate skin on the upper half  of  the back of the leg.
+
+
+
+
+
+
+
+Therefore the complications are mainly related to distal embolization of the arterial tree and lower limb ischemia, which in the most severe cases can lead to leg amputation.
+Ultrasound with duplex Doppler is the most helpful way of diagnosing a popliteal artery aneurysm because it can demonstrate abnormal dilation of the artery, confirm or rule out thrombus within the aneurysm, and help distinguish it from other masses of the popliteal fossa such as a synovial cyst (Baker’s cyst). Popliteal artery aneurysms are usually repaired surgically in view of high risk of thromboembolic complications.
+
+
+611
+Lower Limb
+
+
+
+LEG
+
+The leg is that part of the lower limb between the knee joint and ankle joint (Fig. 6.84):
+
+fibrous joint and forms the lateral malleolus of the ankle joint.
+The tibia is the weight-bearing bone of the leg and is therefore much larger than the fibula. Above, it takes part
+
+
+
+
+■     Proximally, most major structures pass between the thigh and leg through or in relation to the popliteal fossa behind the knee.
+■     Distally, structures pass between the leg and foot mainly through the tarsal tunnel on the posteromedial side of
+
+in the formation of the knee joint and below it forms the medial malleolus and most of the bony surface for articula-tion of the leg with the foot at the ankle joint.
+The leg is divided into anterior (extensor), posterior (flexor), and lateral (fibular) compartments by:
+
+the ankle, the exceptions being the anterior tibial artery	■     an   interosseous   membrane,   which   links   adjacent
+
+and the ends of the deep and superficial fibular nerves, which enter the foot anterior to the ankle.
+
+The bony framework of the leg consists of two bones, the tibia and fibula, arranged in parallel.
+The fibula is much smaller than the tibia and is on the lateral side of  the leg. It articulates superiorly with the inferior aspect of the lateral condyle of the proximal tibia,
+
+borders of the tibia and fibula along most of their length; ■     two intermuscular septa, which pass between the fibula
+and deep fascia surrounding the limb; and
+■     direct  attachment  of  the  deep  fascia  to  the  perios-teum of  the anterior and medial borders of  the tibia (Fig. 6.84).
+
+Muscles in the anterior compartment of the leg dorsiflex
+
+
+
+but does not take part in formation of the knee joint. The distal end of the fibula is firmly anchored to the tibia by a
+
+the ankle, extend the toes, and invert the foot. Muscles in the posterior compartment plantarflex the ankle, flex the toes, and invert the foot. Muscles in the lateral compart-ment evert the foot. Major nerves and vessels supply or pass through each compartment.
+
+
+
+
+
+
+Anterior and posterior intermuscular septa
+
+Anterior
+
+
+Interosseous membrane
+
+Anterior compartment of leg
+
+Bones
+Shaft and distal end of tibia
+The shaft of the tibia is triangular in cross section and has anterior, interosseous, and medial borders and medial, lateral, and posterior surfaces (Fig. 6.85):
+
+
+
+
+
+
+
+Knee joint
+
+Popliteal fossa
+
+Fibula
+
+
+Medial
+
+
+
+
+
+
+
+Deep fascia
+
+■     The anterior and medial borders and the entire medial surface are subcutaneous and easily palpable.
+■     The interosseous border of the tibia is connected, by the interosseous membrane, along its length to the interos-seous border of the fibula.
+■     The posterior surface is marked by an oblique line (the soleal line).
+
+The soleal line descends across the bone from the lateral
+
+
+
+
+Tibia
+
+
+Lateral malleolus
+
+
+Lateral	Posterior compartment	compartment of leg	of leg
+Leg
+
+Ankle joint
+Medial malleolus
+
+Tarsal tunnel
+
+side to the medial side where it merges with the medial border. In addition, a vertical line descends down the upper part of the posterior surface from the midpoint of the soleal line. It disappears in the lower one-third of the tibia.
+The shaft of  the tibia expands at both the upper and lower ends to support the body’s weight at the knee and ankle joints.
+The distal end of the tibia is shaped like a rectangular box with a bony protuberance on the medial side (the
+
+Fig. 6.84  Posterior view of leg; cross section through the left leg 612	(inset).
+
+
+medial malleolus; Fig. 6.81). The upper part of the box is continuous with the shaft of the tibia while the lower
+Regional Anatomy  •  Leg	6
+
+
+
+
+
+Interosseous membrane
+Lateral surface
+Interosseous	Anterior border	border
+
+Soleal line
+
+
+Roughened triangular area that fits into fibular groove of tibia
+
+
+
+Anterior border
+Interosseous border
+
+
+Medial surface
+Anterior border
+
+
+Lateral surface
+
+Fibula
+
+
+
+Tibia
+
+Medial surface
+
+Medial border
+
+C
+
+
+
+Posterior border
+
+Posterior surface Interosseous border
+Medial crest
+Posterior surface
+
+
+Fibular groove on tibia
+
+Articular surfaces for talus
+
+D
+
+
+
+
+
+
+Lateral malleolus
+
+
+
+A
+
+Medial malleolus
+
+Groove for tendon of tibialis posterior muscle
+
+Malleolar fossa
+
+B
+
+
+Lateral malleolus
+
+
+Groove for fibularis longus and brevis muscles
+
+
+Fig. 6.85  Tibia and fibula. A. Anterior view. B. Posterior view. C. Cross section through shafts. D. Posteromedial view of distal ends.
+
+
+
+
+surface and the medial malleolus articulate with one of the tarsal bones (talus) to form a large part of the ankle joint. The posterior surface of the box-like distal end of the tibia is marked by a vertical groove, which continues infe-riorly and medially onto the posterior surface of the medial malleolus. The groove is for the tendon of the tibialis pos-
+terior muscle.
+The lateral surface of the distal end of the tibia is occu-pied by a deep triangular notch (the fibular notch), to which the distal head of the fibula is anchored by a thick-ened part of the interosseous membrane.
+
+Shaft and distal end of fibula
+The fibula is not involved in weight-bearing. The fibular shaft is therefore much narrower than the shaft of  the tibia. Also, and except for the ends, the fibula is enclosed by muscles.
+
+Like the tibia, the shaft of  the fibula is triangular in cross section and has three borders and three surfaces for the attachment of muscles, intermuscular septa, and liga-ments (Fig. 6.85). The interosseous border of  the fibula faces and is attached to the interosseous border of the tibia by the interosseous membrane. Intermuscular septa attach to the anterior and posterior borders. Muscles attach to the three surfaces.
+The narrow medial surface faces the anterior com-partment of the leg, the lateral surface faces the lateral compartment of the leg, and the posterior surface faces the posterior compartment of the leg.
+The  posterior  surface  is  marked  by  a  vertical  crest (medial crest), which divides the posterior surface into two parts each attached to a different deep flexor muscle.
+The distal end of the fibula expands to form the spade-
+shaped lateral malleolus (Fig. 6.85).	613
+Lower Limb
+
+
+
+The medial surface of the lateral malleolus bears a facet for articulation with the lateral surface of the talus, thereby forming the lateral part of the ankle joint. Just superior to this articular facet is a triangular area, which fits into the fibular notch on the distal end of the tibia. Here the tibia and fibula are joined together by the distal end of  the interosseous membrane. Posteroinferior to the facet for articulation with the talus is a pit or fossa (the malleolar fossa) for the attachment of the posterior talofibular liga-ment associated with the ankle joint.
+The posterior surface of the lateral malleolus is marked by a shallow groove for the tendons of the fibularis longus and fibularis brevis muscles.
+
+
+Joints
+Interosseous membrane of leg
+The interosseous membrane of the leg is a tough fibrous sheet of connective tissue that spans the distance between facing interosseous borders of the tibial and fibular shafts (Fig. 6.86). The collagen fibers descend obliquely from the
+
+interosseous border of the tibia to the interosseous border of the fibula, except superiorly where there is a ligamentous band, which ascends from the tibia to fibula.
+There are two apertures in the interosseous membrane, one at the top and the other at the bottom, for vessels to pass between the anterior and posterior compartments of the leg.
+The interosseous membrane not only links the tibia and fibula together, but also provides an increased surface area for muscle attachment.
+The distal ends of the fibula and tibia are held together by the inferior aspect of the interosseous membrane, which spans the narrow space between the fibular notch on the lateral surface of the distal end of the tibia and the cor-responding surface on the distal end of  the fibula. This expanded end of the interosseous membrane is reinforced by anterior and posterior tibiofibular ligaments. This firm linking together of  the distal ends of  the tibia and fibula is essential to produce the skeletal framework for articulation with the foot at the ankle joint.
+
+
+
+
+
+
+
+
+
+
+Aperture for anterior tibial vessels
+
+
+Interosseous membrane
+
+
+
+
+Interosseous membrane
+
+
+
+Posterior tibiofibular ligament
+
+
+B
+
+Aperture for perforating branch of fibular artery
+
+
+Anterior tibiofibular ligament
+
+A
+
+614	Fig. 6.86  Interosseous membrane. A. Anterior view. B. Posteromedial view.
+Regional Anatomy  •  Leg	6
+
+
+
+
+Posterior compartment of leg Muscles
+Muscles in the posterior (flexor) compartment of the leg are organized into two groups, superficial and deep, separated by a layer of  deep fascia. Generally, the muscles mainly plantarflex and invert the foot and flex the toes. All are innervated by the tibial nerve.
+
+Superficial group
+The superficial group of muscles in the posterior compart-ment of the leg comprises three muscles—the gastrocne-mius, plantaris, and soleus (Table 6.6)—all of which insert onto the heel (calcaneus) of the foot and plantarflex the foot at the ankle joint (Fig. 6.87). As a unit, these muscles are  large  and  powerful  because  they  propel  the  body forward off the planted foot during walking and can elevate the body upward onto the toes when standing. Two of the muscles (gastrocnemius and plantaris) originate on the distal end of the femur and can also flex the knee.
+
+Gastrocnemius
+The gastrocnemius muscle is the most superficial of the muscles in the posterior compartment and is one of the largest muscles in the leg (Fig. 6.87). It originates from two heads, one lateral and one medial:
+
+At the knee, the facing margins of the two heads of the gastrocnemius form the lateral and medial borders of the lower end of the popliteal fossa.
+In the upper leg, the heads of the gastrocnemius combine to form a single elongate muscle belly, which forms much of the soft tissue bulge identified as the calf.
+In the lower leg, the muscle fibers of the gastrocnemius converge with those of the deeper soleus muscle to form the calcaneal tendon, which attaches to the calcaneus (heel) of the foot.
+The gastrocnemius plantarflexes the foot at the ankle joint and can also flex the leg at the knee joint. It is inner-vated by the tibial nerve.
+
+Plantaris
+The plantaris has a small muscle belly proximally and a long thin tendon, which descends through the leg and joins the calcaneal tendon (Fig. 6.87). The muscle takes origin superiorly from the lower part of the lateral supra-condylar ridge of the femur and from the oblique popliteal ligament associated with the knee joint.
+The short spindle-shaped muscle body of the plantaris descends medially, deep to the lateral head of the gastroc-nemius, and forms a thin tendon, which passes between the gastrocnemius and soleus muscles and eventually fuses with  the  medial  side  of  the  calcaneal  tendon  near  its attachment to the calcaneus.
+
+
+
+■     The medial head is attached to an elongate roughen-ing on the posterior aspect of  the distal femur just behind the adductor tubercle and above the articular surface of the medial condyle.
+■     The lateral head originates from a distinct facet on the upper  lateral  surface  of  the  lateral  femoral  condyle where it joins the lateral supracondylar line.
+
+The plantaris contributes to plantarflexion of the foot at the ankle joint and flexion of the leg at the knee joint, and is innervated by the tibial nerve.
+
+Soleus
+The soleus is a large flat muscle under the gastrocnemius muscle (Fig. 6.87). It is attached to the proximal ends of
+
+
+
+
+Table 6.6    Superficial group of muscles in the posterior compartment of leg (spinal segments in bold are the major segments innervating the muscle)
+
+
+Muscle Gastrocnemius
+
+
+
+Plantaris
+
+
+Soleus
+
+Origin
+Medial head—posterior surface of distal femur just superior to medial condyle; lateral head—upper posterolateral surface of lateral femoral condyle
+Inferior part of lateral supracondylar line of femur and oblique popliteal ligament of knee
+Soleal line and medial border of tibia; posterior aspect of fibular head and adjacent surfaces of neck and proximal shaft; tendinous arch between tibial and fibular attachments
+
+Insertion
+Via calcaneal tendon, to posterior surface of calcaneus
+
+
+
+Via calcaneal tendon, to posterior surface of calcaneus
+
+Via calcaneal tendon, to posterior surface of calcaneus
+
+Innervation
+Tibial nerve (S1, S2)
+
+
+
+
+Tibial nerve (S1, S2)
+
+
+Tibial nerve (S1, S2)
+
+Function
+Plantarflexes foot and flexes knee
+
+
+
+Plantarflexes foot and flexes knee
+
+Plantarflexes the foot
+
+
+
+
+615
+Lower Limb
+
+
+
+
+
+
+Medial head of gastrocnemius
+
+
+Plantaris
+
+Lateral head of gastrocnemius
+
+
+
+
+
+
+
+Popliteal vessels and tibial nerve
+
+
+Soleus
+
+Ligament spanning distance between fibular and tibial origins of soleus
+
+
+
+
+
+Gastrocnemius
+
+
+
+
+
+Medial
+
+
+
+
+
+
+
+Tendon of plantaris
+
+Lateral
+
+
+
+
+Gastrocnemius
+
+Calcaneal (Achilles) tendon
+
+
+Soleus
+
+Calcaneus
+
+
+
+
+
+
+
+
+
+Calcaneal tendon
+
+
+Calcaneus A	B
+
+Fig. 6.87  Superficial group of muscles in the posterior compartment of leg. A. Posterior view. B. Lateral view.
+
+
+
+
+616
+Regional Anatomy  •  Leg	6
+
+
+the fibula and tibia, and to a tendinous ligament, which spans the distance between the two heads of attachment to the fibula and tibia:
+Soleal line
+
+■     On the proximal end of the fibula, the soleus originates from the posterior aspect of  the head and adjacent surface of the neck and upper shaft of the fibula.
+■     On the tibia, the soleus originates from the soleal line and adjacent medial border.
+■     The ligament, which spans the distance between the attachments to the tibia and fibula, arches over the popliteal vessels and tibial nerve as they pass from the popliteal fossa into the deep region of  the posterior compartment of the leg.
+
+In the lower leg, the soleus muscle narrows to join the
+
+
+
+
+
+
+Popliteus
+
+
+
+
+
+Tibialis posterior
+
+
+Origin of flexor digitorum longus
+
+
+
+
+
+
+
+Vertical line
+Origin of tibialis posterior
+
+
+
+calcaneal tendon that attaches to the calcaneus.
+The soleus muscle, together with the gastrocnemius and plantaris, plantarflexes the foot at the ankle joint. It is innervated by the tibial nerve.
+
+
+
+In the clinic
+
+Calcaneal (Achilles) tendon rupture
+Rupture of the calcaneal tendon is often related to sudden or direct trauma. This type of injury frequently occurs in a normal healthy tendon. In addition, there are certain conditions that may predispose the tendon to rupture. Among these conditions are tendinopathy (due to overuse, or to age-related degenerative changes) and previous calcaneal tendon interventions such as injections of pharmaceuticals and the use of certain antibiotics (quinolone group). The diagnosis of calcaneal tendon rupture is relatively straightforward. The patient typically complains of “being kicked” or “shot” behind the ankle, and clinical examination often reveals a gap in the tendon.
+
+
+
+Deep group
+There are four muscles in the deep posterior compartment of the leg (Fig. 6.88)—the popliteus, flexor hallucis longus, flexor digitorum longus, and tibialis posterior (Table 6.7). The popliteus muscle acts on the knee, whereas the other three muscles act mainly on the foot.
+
+Popliteus
+
+
+
+Flexor digitorum longus
+
+
+
+Flexor hallucis longus
+
+
+
+
+Medial
+
+
+
+Groove on medial malleolus
+
+Tuberosity of navicular
+
+Medial cuneiform
+
+
+
+
+
+
+
+
+
+
+
+Origin of flexor hallucis longus
+
+
+Lateral
+
+
+
+Groove on posterior surface of talus
+
+Groove on inferior surface of sustentaculum tali of calcaneus bone
+
+
+
+The popliteus is the smallest and most superior of  the deep muscles in the posterior compartment of the leg. It unlocks the extended knee at the initiation of flexion and stabilizes the knee by resisting lateral (external) rotation of the tibia on the femur. It is flat and triangular in shape,
+
+Fig. 6.88  Deep group of muscles in the posterior compartment of leg.
+
+
+
+617
+Lower Limb
+
+
+Table 6.7    Deep group of muscles in the posterior compartment of leg (spinal segments in bold are the major segments innervating the muscle)
+
+
+Muscle Popliteus
+
+
+
+Flexor hallucis longus
+Flexor digitorum longus
+
+Tibialis posterior
+
+Origin
+Lateral femoral condyle
+
+
+
+Posterior surface of fibula and adjacent interosseous membrane
+Medial side of posterior surface of the tibia
+
+Posterior surfaces of interosseous membrane and adjacent regions of tibia and fibula
+
+Insertion
+Posterior surface of proximal tibia
+
+
+Plantar surface of distal phalanx of great toe
+Plantar surfaces of bases of distal phalanges of the lateral four toes
+Mainly to tuberosity of navicular and adjacent region of medial cuneiform
+
+Innervation
+Tibial nerve (L4 to S1)
+
+
+
+Tibial nerve (S2, S3)
+
+Tibial nerve (S2, S3)
+
+
+Tibial nerve (L4, L5)
+
+Function
+Stabilizes knee joint (resists lateral rotation of tibia on femur) Unlocks knee joint (laterally rotates femur on fixed tibia)
+Flexes great toe
+
+Flexes lateral four toes
+
+
+Inversion and plantarflexion of foot; support of medial arch of foot during walking
+
+
+
+
+
+
+
+forms part of the floor of the popliteal fossa (Fig. 6.88), and is inserted into a broad triangular region above the soleal line on the posterior surface of the tibia.
+The popliteus muscle ascends laterally across the lower aspect of  the knee and originates from a tendon, which penetrates the fibrous membrane of the joint capsule of the knee. The tendon ascends laterally around the joint where it passes between the lateral meniscus and the fibrous membrane and then into a groove on the inferolateral aspect of the lateral femoral condyle. The tendon attaches to and originates from a depression at the anterior end of the groove.
+When initiating gait from a standing position, contrac-tion of the popliteus laterally rotates the femur on the fixed tibia, unlocking the knee joint. The popliteus muscle is innervated by the tibial nerve.
+
+Flexor hallucis longus
+The flexor hallucis longus muscle originates on the lateral side of the posterior compartment of the leg and inserts into the plantar surface of the great toe on the medial side of the foot (Fig. 6.88). It arises mainly from the lower two-thirds of the posterior surface of the fibula and adjacent interosseous membrane.
+The muscle fibers of the flexor hallucis longus converge inferiorly to form a large cord-like tendon, which passes behind the distal head of  the tibia and then slips into a distinct groove on the posterior surface of  the adjacent tarsal bone (talus) of the foot. The tendon curves anteriorly first under the talus and then under a shelf of bone (the sustentaculum tali), which projects medially from the cal-caneus, and then continues anteriorly through the sole of the foot to insert on the inferior surface of the base of the
+618	distal phalanx of the great toe.
+
+The flexor hallucis longus flexes the great toe. It is par-ticularly active during the toe-off phase of walking when the body is propelled forward off  the stance leg and the great toe is the last part of the foot to leave the ground. It can also contribute to plantarflexion of  the foot at the ankle joint and is innervated by the tibial nerve.
+
+Flexor digitorum longus
+The  flexor  digitorum  longus  muscle  originates  on  the medial side of the posterior compartment of the leg and inserts into the lateral four digits of the foot (Fig. 6.88). It arises mainly from the medial side of the posterior surface of the tibia inferior to the soleal line.
+The flexor digitorum longus descends in the leg and forms a tendon, which crosses posterior to the tendon of the  tibialis  posterior  muscle  near  the  ankle  joint. The tendon continues inferiorly in a shallow groove behind the medial malleolus and then swings forward to enter the sole of the foot. It crosses inferior to the tendon of the flexor hallucis longus muscle to reach the medial side of the foot and then divides into four tendons, which insert on the plantar surfaces of  the bases of  the distal phalanges of digits II to V.
+The flexor digitorum longus flexes the lateral four toes. It is involved with gripping the ground during walking and propelling the body forward off the toes at the end of the stance phase of gait. It is innervated by the tibial nerve.
+
+Tibialis posterior
+The tibialis posterior muscle originates from the interosse-ous membrane and the adjacent posterior surfaces of the tibia and fibula (Fig. 6.88). It lies between and is overlapped by  the  flexor  digitorum  longus  and  the  flexor  hallucis longus muscles.
+Regional Anatomy  •  Leg	6
+
+
+
+Near the ankle, the tendon of  the tibialis posterior is crossed superficially by the tendon of the flexor digitorum longus muscle and lies medial to this tendon in the groove on the posterior surface of the medial malleolus. The tendon curves forward under the medial malleolus and enters the medial side of the foot. It wraps around the medial margin
+
+of the foot to attach to the plantar surfaces of the medial tarsal bones, mainly to the tuberosity of the navicular and to the adjacent region of the medial cuneiform.
+The tibialis posterior inverts and plantarflexes the foot, and supports the medial arch of the foot during walking. It is innervated by the tibial nerve.
+
+
+
+
+
+
+
+In the clinic
+
+Neurological examination of the legs
+Some of the commonest conditions that affect the legs are peripheral neuropathy (particularly associated with diabetes mellitus), lumbar nerve root lesions (associated with pathology of the intervertebral discs), fibular nerve palsy, and spastic paraparesis.
+
+■     Look for muscle wasting—loss of muscle mass may indicate loss of or reduced innervation.
+■     Test the power in muscle groups—hip flexion (L1,
+L2—iliopsoas—straight leg raise); knee flexion (L5 to S2—hamstrings—the patient tries to bend the knee while the examiner applies force to the leg to hold the knee in extension); knee extension (L3, L4—quadriceps femoris—the patient attempts to keep the leg straight
+
+
+
+while the examiner applies a force to the leg to flex the knee joint); ankle plantarflexion (S1, S2—the patient pushes the foot down while the examiner applies a force to the plantar surface of the foot to dorsiflex the ankle joint); ankle dorsiflexion (L4, L5—the patient pulls the foot upward while the examiner applies a force to the dorsal aspect of the foot to plantarflex the ankle joint).
+■     Examine knee and ankle reflexes—a tap with a tendon hammer on the patellar ligament (tendon) tests reflexes at the L3–L4 spinal levels, and tapping the calcaneal tendon tests reflexes at the S1–S2 spinal levels.
+■     Assess status of general sensory input to lumbar and upper sacral spinal cord levels—test light touch, pin prick, and vibration sense at dermatomes in the lower limb.
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+619
+Lower Limb
+
+
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+
+Arteries Popliteal artery
+The popliteal artery is the major blood supply to the leg and foot and enters the posterior compartment of the leg from the popliteal fossa behind the knee (Fig. 6.89).
+The popliteal artery passes into the posterior compart-ment of the leg between the gastrocnemius and popliteus muscles. As it continues inferiorly it passes under the ten-dinous arch formed between the fibular and tibial heads of the soleus muscle and enters the deep region of the poste-rior compartment of the leg where it immediately divides into an anterior tibial artery and a posterior tibial artery.
+Two large sural arteries, one on each side, branch from the popliteal artery to supply the gastrocnemius, soleus, and plantaris muscles (Fig. 6.89). In addition, the popliteal artery gives rise to branches that contribute to a collateral network of vessels around the knee joint (see Fig. 6.80).
+
+Anterior tibial artery
+The anterior tibial artery passes forward through the aperture in the upper part of the interosseous membrane and enters and supplies the anterior compartment of the leg. It continues inferiorly onto the dorsal aspect of  the foot.
+
+Posterior tibial artery
+The posterior tibial artery supplies the posterior and lateral compartments of the leg and continues into the sole of the foot (Fig. 6.89).
+The posterior tibial artery descends through the deep region of  the posterior compartment of  the leg on the superficial surfaces of the tibialis posterior and flexor digi-torum longus muscles. It passes through the tarsal tunnel behind the medial malleolus and into the sole of the foot.
+In the leg, the posterior tibial artery supplies adjacent muscles and bone and has two major branches, the cir-cumflex fibular artery and the fibular artery:
+
+
+Adductor magnus muscle
+
+
+Adductor hiatus
+
+
+
+
+
+Superior medial genicular artery
+
+Medial head of gastrocnemius
+muscle
+
+
+Popliteus muscle
+
+Posterior tibial artery
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+
+Posterior tibial artery
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+
+Popliteal vein
+
+
+Popliteal artery
+Superior lateral genicular artery
+Sural arteries
+
+
+
+Circumflex fibular artery
+
+Anterior tibial artery (passes through aperture in interosseous membrane)
+
+Fibular artery
+
+
+
+
+
+
+
+Branches that perforate intermuscular septum to enter lateral compartment
+
+Perforating terminal branch of fibular artery
+
+
+■     The circumflex fibular artery passes laterally through the soleus muscle and around the neck of the fibula to connect with the anastomotic network of vessels sur-rounding the knee (Fig. 6.89; see also Fig. 6.80).
+■     The fibular artery parallels the course of  the tibial artery, but descends along the lateral side of the poste-
+rior compartment adjacent to the medial crest on the	Fig. 6.89  Arteries in the posterior compartment of leg. posterior  surface  of  the  fibula,  which  separates  the
+attachments of the tibialis posterior and flexor hallucis longus muscles.
+
+The  fibular  artery  supplies  adjacent  muscles  and 620	bone in the posterior compartment of the leg and also has
+Regional Anatomy  •  Leg	6
+
+
+
+branches that pass laterally through the intermuscular septum to supply the fibularis muscles in the lateral com-partment of the leg.
+A perforating branch that originates from the fibular artery distally in the leg passes anteriorly through the inferior aperture in the interosseous membrane to anasto-mose with a branch of the anterior tibial artery.
+The  fibular  artery  passes  behind  the  attachment between the distal ends of the tibia and fibula and termi-nates in a network of vessels over the lateral surface of the calcaneus.
+
+Veins
+Deep veins in the posterior compartment generally follow the arteries.
+
+Nerves Tibial nerve
+
+The nerve associated with the posterior compartment of the leg is the tibial nerve (Fig. 6.90), a major branch of the sciatic nerve that descends into the posterior compartment from the popliteal fossa.
+The tibial nerve passes under the tendinous arch formed between the fibular and tibial heads of the soleus muscle and passes vertically through the deep region of the poste-rior compartment of the leg on the surface of the tibialis posterior muscle with the posterior tibial vessels.
+The tibial nerve leaves the posterior compartment of the leg at the ankle by passing through the tarsal tunnel behind the medial malleolus. It enters the foot to supply most intrinsic muscles and skin.
+In the leg, the tibial nerve gives rise to:
+
+
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+
+Adductor hiatus
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+Tibial nerve
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+Sciatic nerve
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+Sural nerve
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+Common fibular nerve
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+Sural nerve
+
+
+
+■     branches that supply all the muscles in the posterior compartment of the leg, and
+■     two cutaneous branches, the sural nerve and medial calcaneal nerve.
+
+
+
+
+Penetrates deep fascia
+
+
+
+Medial calcaneal nerve
+
+
+
+
+
+
+A	B
+
+Fig. 6.90  Tibial nerve. A. Posterior view. B. Sural nerve.
+621
+Lower Limb
+
+
+
+Branches of the tibial nerve that innervate the superfi-cial group of muscles of the posterior compartment and popliteus muscle of the deep group originate high in the leg between the two heads of the gastrocnemius muscle in the distal region of the popliteal fossa (Fig. 6.91). Branches innervate the gastrocnemius, plantaris, and soleus muscles, and pass more deeply into the popliteus muscle.
+Branches to the deep muscles of the posterior compart-ment originate from the tibial nerve deep to the soleus muscle in the upper half of the leg and innervate the tibi-alis posterior, flexor hallucis longus, and flexor digitorum longus muscles.
+
+Sural nerve
+The sural nerve originates high in the leg between the two heads of the gastrocnemius muscle (Fig. 6.90). It descends superficial to the belly of the gastrocnemius muscle and penetrates through the deep fascia approximately in the
+
+
+Fibularis longus
+The fibularis longus muscle arises in the lateral compart-ment of the leg, but its tendon crosses under the foot to attach to bones on the medial side (Fig. 6.91). It originates from both the upper lateral surface of the fibula and from
+
+
+
+
+Common fibular nerve
+
+
+
+
+
+
+Interosseous membrane
+
+
+
+middle of the leg where it is joined by a sural communicat-ing branch from the common fibular nerve. It passes down the leg, around the lateral malleolus, and into the foot.
+The sural nerve supplies skin on the lower posterolat-eral surface of the leg and the lateral side of the foot and little toe.
+
+Medial calcaneal nerve
+The medial calcaneal nerve is often multiple and originates from the tibial nerve low in the leg near the ankle and descends onto the medial side of the heel.
+The  medial  calcaneal  nerve  innervates  skin  on  the medial surface and sole of the heel (Fig. 6.90).
+
+
+Lateral compartment of leg Muscles
+There are two muscles in the lateral compartment of the leg—the fibularis longus and fibularis brevis (Fig. 6.91 and
+
+
+Fibularis longus
+
+
+
+
+
+Fibularis brevis
+
+
+
+
+
+
+
+
+
+
+A
+
+
+Anterior
+border of fibula
+
+
+
+Groove on inferior aspect of cuboid
+Medial cuneiform
+Metatarsal I
+
+
+
+B
+
+
+
+
+Fibular trochlea
+of calcaneus bone
+
+
+
+
+
+
+Fibularis brevis tendon
+
+Fibularis longus tendon
+
+
+
+Table 6.8). Both evert the foot (turn the sole outward) and are innervated by the superficial fibular nerve, which is a branch of the common fibular nerve.
+
+
+Fig. 6.91  Muscles in the lateral compartment of leg. A. Lateral view. B. Inferior view of the right foot, with the foot plantarflexed at the ankle.
+
+
+
+
+
+
+Table 6.8    Muscles of the lateral compartment of leg (spinal segments in bold are the major segments innervating the muscle)
+
\ No newline at end of file