Human Anatomy

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The muscles of the lower extremity are subdivided into groups corresponding with the different regions of the limb.
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I. Muscles of the Iliac Region.


III. Muscles of the Leg.

II. Muscles of the Thigh.


IV. Muscles of the Foot.


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8c. The Muscles and Fasciæ of the Leg





The muscles of the leg may be divided into three groups: anterior, posterior, and lateral.
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1. [b]The Anterior Crural Muscles (Fig. 437).[/b]





Tibialis anterior.


Extensor digitorum longus.

Extensor hallucis longus.


Peronæus tertius.



Deep Fascia (fascia cruris).—The deep fascia of the leg forms a complete investment to the muscles, and is fused with the periosteum over the subcutaneous surfaces of the bones. It is continuous above with the fascia lata, and is attached around the knee to the patella, the ligamentum patellæ, the tuberosity and condyles of the tibia, and the head of the tibula. Behind, it forms the popliteal fascia, covering in the popliteal fossa; here it is strengthened by transverse fibers, and perforated by the small saphenous vein. It receives an expansion from the tendon of the Biceps femoris laterally, and from the tendons of the Sartorius, Gracilis, Semitendinosus, and Semimembranosus medially; in front, it blends with the periosteum covering the subcutaneous surface of the tibia, and with that covering the head and malleolus of the fibula; below, it is continuous with the transverse crural and laciniate ligaments. It is thick and dense in the upper and anterior part of the leg, and gives attachment, by its deep surface, to the Tibialis anterior and Extensor digitorum longus; but thinner behind, where it covers the Gastrocnemius and Soleus. It gives off from its deep surface, on the lateral side of the leg, two strong intermuscular septa, the anterior and posterior peroneal septa, which enclose the Peronæi longus and brevis, and separate them from the muscles of the anterior and posterior crural regions, and several more slender processes which enclose the individual muscles in each region. A broad transverse intermuscular septum, called the deep transverse fascia of the leg, intervenes between the superficial and deep posterior crural muscles.
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The Tibialis anterior (Tibialis anticus) is situated on the lateral side of the tibia; it is thick and fleshy above, tendinous below. It arises from the lateral condyle and upper half or two-thirds of the lateral surface of the body of the tibia; from the adjoining part of the interosseous membrane; from the deep surface of the fascia; and from the intermuscular septum between it and the Extensor digitorum longus. The fibers run vertically downward, and end in a tendon, which is apparent on the anterior surface of the muscle at the lower third of the leg. After passing through the most medial compartments of the transverse and cruciate crural ligaments, it is inserted into the medial and under surface of the first cuneiform bone, and the base of the first metatarsal bone. This muscle overlaps the anterior tibial vessels and deep peroneal nerve in the upper part of the leg.
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Variations.—A deep portion of the muscle is rarely inserted into the talus, or a tendinous slip may pass to the head of the first metatarsal bone or the base of the first phalanx of the great toe. The Tibiofascialis anterior, a small muscle from the lower part of the tibia to the transverse or cruciate crural ligaments or deep fascia.
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The Extensor hallucis longus (Extensor proprius hallucis) is a thin muscle, situated between the Tibialis anterior and the Extensor digitorum longus. It arises from the anterior surface of the fibula for about the middle two-fourths of its extent, medial to the origin of the Extensor digitorum longus; it also arises from the interosseous membrane to a similar extent. The anterior tibial vessels and deep peroneal nerve lie between it and the Tibialis anterior. The fibers pass downward, and end in a tendon, which occupies the anterior border of the muscle, passes through a distinct compartment in the cruciate crural ligament, crosses from the lateral to the medial side of the anterior tibial vessels near the bend of the ankle, and is inserted into the base of the distal phalanx of the great toe. Opposite the metatarsophalangeal articulation, the tendon gives off a thin prolongation on either side, to cover the surface of the joint. An expansion from the medial side of the tendon is usually inserted into the base of the proximal phalanx.
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Variations.—Occasionally united at its origin with the Extensor digitorum longus. Extensor ossis metatarsi hallucis, a small muscle, sometimes found as a slip from the Extensor hallucis longus, or from the Tibialis anterior, or from the Extensor digitorum longus, or as a distinct muscle; it traverses the same compartment of the transverse ligament with the Extensor hallucis longus.
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FIG. 437– Muscles of the front of the leg. (See enlarged image)



The Extensor digitorum longus is a penniform muscle, situated at the lateral part of the front of the leg. It arises from the lateral condyle of the tibia; from the upper three-fourths of the anterior surface of the body of the fibula; from the upper part of the interosseous membrane; from the deep surface of the fascia; and from the intermuscular septa between it and the Tibialis anterior on the medial, and the Peronæi on the lateral side. Between it and the Tibialis anterior are the upper portions of the anterior tibial vessels and deep peroneal nerve. The tendon passes under the transverse and cruciate crural ligaments in company with the Peronæus tertius, and divides into four slips, which run forward on the dorsum of the foot, and are inserted into the second and third phalanges of the four lesser toes. The tendons to the second, third, and fourth toes are each joined, opposite the metatarsophalangeal articulation, on the lateral side by a tendon of the Extensor digitorum brevis. The tendons are inserted in the following manner: each receives a fibrous expansion from the Interossei and Lumbricalis, and then spreads out into a broad aponeurosis, which covers the dorsal surface of the first phalanx: this aponeurosis, at the articulation of the first with the second phalanx, divides into three slips—an intermediate, which is inserted into the base of the second phalanx; and two collateral slips, which, after uniting on the dorsal surface of the second phalanx, are continued onward, to be inserted into the base of the third phalanx.
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Variations.—This muscle varies considerably in the modes of origin and the arrangement of its various tendons. The tendons to the second and fifth toes may be found doubled, or extra slips are given off from one or more tendons to their corresponding metatarsal bones, or to the short extensor, or to one of the interosseous muscles. A slip to the great toe from the innermost tendon has been found.
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The Peronæus tertius is a part of the Extensor digitorum longus, and might be described as its fifth tendon. The fibers belonging to this tendon arise from the lower third or more of the anterior surface of the fibula; from the lower part of the interosseous membrane; and from an intermuscular septum between it and the Peronæus brevis. The tendon, after passing under the transverse and cruciate crural ligaments in the same canal as the Extensor digitorum longus, is inserted into the dorsal surface of the base of the metatarsal bone of the little toe. This muscle is sometimes wanting.
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Nerves.—These muscles are supplied by the fourth and fifth lumbar and first sacral nerves through the deep peroneal nerve.
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Actions.—The Tibialis anterior and Peronæus tertius are the direct flexors of the foot at the ankle-joint; the former muscle, when acting in conjunction with the Tibialis posterior, raises the medial border of the foot, i. e., inverts the foot; and the latter, acting with the Peronæi brevis and longus, raises the lateral border of the foot, i. e., everts the foot. The Extensor digitorum longus and Extensor hallucis longus extend the phalanges of the toes, and, continuing their action, flex the foot upon the leg. Taking their fixed points from below, in the erect posture, all these muscles serve to fix the bones of the leg in the perpendicular position, and give increased strength to the ankle-joint.
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2. [b]The Posterior Crural Muscles—The muscles of the back of the leg are subdivided into two groups—superficial and deep. Those of the superficial group constitute a powerful muscular mass, forming the calf of the leg. Their large size is one of the most characteristic features of the muscular apparatus in man, and bears a direct relation to his erect attitude and his mode of progression.[/b]
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[b]The Superficial Group (Fig. 438).[/b]





Gastrocnemius.
Soleus.
Plantaris.

The Gastrocnemius is the most superficial muscle, and forms the greater part of the calf. It arises by two heads, which are connected to the condyles of the femur by strong, flat tendons. The medial and larger head takes its origin from a depression at the upper and back part of the medial condyle and from the adjacent part of the femur. The lateral head arises from an impression on the side of the lateral condyle and from the posterior surface of the femur immediately above the lateral part of the condyle. Both heads, also, arise from the subjacent part of the capsule of the knee. Each tendon spreads out into an aponeurosis, which covers the posterior surface of that portion of the muscle to which it belongs. From the anterior surfaces of these tendinous expansions, muscular fibers are given off; those of the medial head being thicker and extending lower than those of the lateral. The fibers unite at an angle in the middle line of the muscle in a tendinous raphé, which expands into a broad aponeurosis on the anterior surface of the muscle, and into this the remaining fibers are inserted. The aponeurosis, gradually contracting, unites with the tendon of the Soleus, and forms with it the tendo calcaneus.
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Variations.—Absence of the outer head or of the entire muscle. Extra slips from the popliteal surface of the femur.
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The Soleus is a broad flat muscle situated immediately in front of the Gastrocnemius. It arises by tendinous fibers from the back of the head of the fibula, and from the upper third of the posterior surface of the body of the bone; from the popliteal line, and the middle third of the medial border of the tibia; some fibers also arise from a tendinous arch placed between the tibial and fibular origins of the muscle, in front of which the popliteal vessels and tibial nerve run. The fibers end in an aponeurosis which covers the posterior surface of the muscle, and, gradually becoming thicker and narrower, joins with the tendon of the Gastrocnemius, and forms with it the tendo calcaneus.
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Variations.—Accessory head to its lower and inner part usually ending in the tendocalcaneus, or the calcaneus, or the laciniate ligament.
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The Gastrocnemius and Soleus together form a muscular mass which is occasionally described as the Triceps suræ; its tendon of insertion is the tendo calcaneus.
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Tendo Calcaneus (tendo Achillis).—The tendo calcaneus, the common tendon of the Gastrocnemius and Soleus, is the thickest and strongest in the body. It is about 15 cm. long, and begins near the middle of the leg, but receives fleshy fibers on its anterior surface, almost to its lower end. Gradually becoming contracted below, it is inserted into the middle part of the posterior surface of the calcaneus, a bursa being interposed between the tendon and the upper part of this surface. The tendon spreads out somewhat at its lower end, so that its narrowest part is about 4 cm. above its insertion. It is covered by the fascia and the integument, and is separated from the deep muscles and vessels by a considerable interval filled up with areolar and adipose tissue. Along its lateral side, but superficial to it, is the small saphenous vein.
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The Plantaris is placed between the Gastrocnemius and Soleus. It arises from the lower part of the lateral prolongation of the linea aspera, and from the oblique popliteal ligament of the knee-joint. It forms a small fusiform belly, from 7 to 10 cm. long, ending in a long slender tendon which crosses obliquely between the two muscles of the calf, and runs along the medial border of the tendo calcaneus, to be inserted with it into the posterior part of the calcaneus. This muscle is sometimes double, and at other times wanting. Occasionally, its tendon is lost in the laciniate ligament, or in the fascia of the leg.
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Nerves.—The Gastrocnemius and Soleus are supplied by the first and second sacral nerves, and the Plantaris by the fourth and fifth lumbar and first sacral nerves, through the tibial nerve.
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Actions.—The muscles of the calf are the chief extensors of the foot at the ankle-joint. They possess considerable power, and are constantly called into use in standing, walking, dancing, and leaping; hence the large size they usually present. In walking, these muscles raise the heel from the ground; the body being thus supported on the raised foot, the opposite limb can be carried forward. In standing, the Soleus, taking its fixed point from below, steadies the leg upon the foot and prevents the body from falling forward. The Gastrocnemius, acting from below, serves to flex the femur upon the tibia, assisted by the Popliteus. The Plantaris is the rudiment of a large muscle which in some of the lower animals is continued over the calcaneus to be inserted into the plantar aponeurosis. In man it is an accessory to the Gastrocnemius, extending the ankle if the foot be free, or bending the knee if the foot be fixed.
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[b]The Deep Group (Fig. 439).[/b]





Popliteus.


Flexor digitorum longus.

Flexor hallucis longus.


Tibialis posterior.



Deep Transverse Fascia.—The deep transverse fascia of the leg is a transversely placed, intermuscular septum, between the superficial and deep muscles of the back of the leg. At the sides it is connected to the margins of the tibia and fibula. Above, where it covers the Popliteus, it is thick and dense, and receives an expansion from the tendon of the Semimembranosus; it is thinner in the middle of the leg; but below, where it covers the tendons passing behind the malleoli, it is thickened and continuous with the laciniate ligament.
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FIG. 438– Muscles of the back of the leg. Superficial layer. (See enlarged image)





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FIG. 439– Muscles of the back of the leg. Deep layer. (See enlarged image)



The Popliteus is a thin, flat, triangular muscle, which forms the lower part of the floor of the popliteal fossa. It arises by a strong tendon about 2.5 cm. long, from a depression at the anterior part of the groove on the lateral condyle of the femur, and to a small extent from the oblique popliteal ligament of the knee-joint; and is inserted into the medial two-thirds of the triangular surface above the popliteal line on the posterior surface of the body of the tibia, and into the tendinous expansion covering the surface of the muscle.
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Variations.—Additional head from the sesamoid bone in the outer head of the Gastrocnemius. Popliteus minor, rare, origin from femur on the inner side of the Plantaris, insertion into the posterior ligament of the knee-joint. Peroneotibialis, 14 per cent., origin inner side of the head of the fibula, insertion into the upper end of the oblique line of the tibia, it lies beneath the Popliteus.
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The Flexor hallucis longus is situated on the fibular side of the leg. It arises from the inferior two-thirds of the posterior surface of the body of the fibula, with the exception of 2.5 cm. at its lowest part; from the lower part of the interosseous membrane; from an intermuscular septum between it and the Peronæi, laterally, and from the fascia covering the Tibialis posterior, medially. The fibers pass obliquely downward and backward, and end in a tendon which occupies nearly the whole length of the posterior surface of the muscle. This tendon lies in a groove which crosses the posterior surface of the lower end of the tibia, the posterior surface of the talus, and the under surface of the sustentaculum tali of the calcaneus; in the sole of the foot it runs forward between the two heads of the Flexor hallucis brevis, and is inserted into the base of the last phalanx of the great toe. The grooves on the talus and calcaneus, which contain the tendon of the muscle, are converted by tendinous fibers into distinct canals, lined by a mucous sheath. As the tendon passes forward in the sole of the foot, it is situated above, and crosses from the lateral to the medial side of the tendon of the Flexor digitorum longus, to which it is connected by a fibrous slip.
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Variations.—Usually a slip runs to the Flexor digitorum and frequently an additional slip runs from the Flexor digitorum to the Flexor hallucis. Peroneocalcaneus internus, rare, origin below or outside the Flexor hallucis from the back of the fibula, passes over the sustentaculum tali with the Flexor hallucis and is inserted into the calcaneum.
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The Flexor digitorum longus is situated on the tibial side of the leg. At its origin it is thin and pointed, but it gradually increases in size as it descends. It arises from the posterior surface of the body of the tibia, from immediately below the popliteal line to within 7 or 8 cm. of its lower extremity, medial to the tibial origin of the Tibialis posterior; it also arises from the fascia covering the Tibialis posterior. The fibers end in a tendon, which runs nearly the whole length of the posterior surface of the muscle. This tendon passes behind the medial malleolus, in a groove, common to it and the Tibialis posterior, but separated from the latter by a fibrous septum, each tendon being contained in a special compartment lined by a separate mucous sheath. It passes obliquely forward and lateralward, superficial to the deltoid ligament of the ankle-joint, into the sole of the foot (Fig. 444), where it crosses below the tendon of the Flexor hallucis longus, and receives from it a strong tendinous slip. It then expands and is joined by the Quadratus plantæ, and finally divides into four tendons, which are inserted into the bases of the last phalanges of the second, third, fourth, and fifth toes, each tendon passing through an opening in the corresponding tendon of the Flexor digitorum brevis opposite the base of the first phalanx.
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Variations.—Flexor accessorius longus digitorum, not infrequent, origin from fibula, or tibia, or the deep fascia and ending in a tendon which, after passing beneath the laciniate ligament, joins the tendon of the long flexor or the Quadratus plantæ.
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The Tibialis posterior (Tibialis posticus) lies between the two preceding muscles, and is the most deeply seated of the muscles on the back of the leg. It begins above by two pointed processes, separated by an angular interval through which the anterior tibial vessels pass forward to the front of the leg. It arises from the whole of the posterior surface of the interosseous membrane, excepting its lowest part; from the lateral portion of the posterior surface of the body of the tibia, between the commencement of the popliteal line above and the junction of the middle and lower thirds of the body below; and from the upper two-thirds of the medial surface of the fibula; some fibers also arise from the deep transverse fascia, and from the intermuscular septa separating it from the adjacent muscles. In the lower fourth of the leg its tendon passes in front of that of the Flexor digitorum longus and lies with it in a groove behind the medial malleolus, but enclosed in a separate sheath; it next passes under the laciniate and over the deltoid ligament into the foot, and then beneath the plantar calcaneonavicular ligament. The tendon contains a sesamoid fibrocartilage, as it runs under the plantar calcaneonavicular ligament. It is inserted into the tuberosity of the navicular bone, and gives off fibrous expansions, one of which passes backward to the sustentaculum tali of the calcaneus, others forward and lateralward to the three cuneiforms, the cuboid, and the bases of the second, third, and fourth metatarsal bones.
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Nerves.—The Popliteus is supplied by the fourth and fifth lumbar and first sacral nerves, the Flexor digitorum longus and Tibialis posterior by the fifth lumbar and first sacral, and the Flexor hallucis longus by the fifth lumbar and the first and second sacral nerves, through the tibial nerve.
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Actions.—The Popliteus assists in flexing the leg upon the thigh; when the leg is flexed, it will rotate the tibia inward. It is especially called into action at the beginning of the act of bending the knee, inasmuch as it produces the slight inward rotation of the tibia which is essential in the early stage of this movement. The Tibialis posterior is a direct extensor of the foot at the ankle-joint; acting in conjunction with the Tibialis anterior, it turns the sole of the foot upward and medialward, i.e., inverts the foot, antagonizing the Peronæi, which turn it upward and lateralward (evert it). In the sole of the foot the tendon of the Tibialis posterior lies directly below the plantar calcaneonavicular ligament, and is therefore an important factor in maintaining the arch of the foot. The Flexor digitorum longus and Flexor hallucis longus are the direct flexors of the phalanges, and, continuing their action, extend the foot upon the leg; they assist the Gastrocnemius and Soleus in extending the foot, as in the act of walking, or in standing on tiptoe. In consequence of the oblique direction of its tendons the Flexor digitorum longus would draw the toes medialward, were it not for the Quadratus plantæ, which is inserted into the lateral side of the tendon, and draws it to the middle line of the foot. Taking their fixed point from the foot, these muscles serve to maintain the upright posture by steadying the tibia and fibula perpendicularly upon the talus.
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3. [b]The Lateral Crural Muscles (Fig. 439).[/b]





Peronæus longus.


Peronæus brevis.

The Peronæus longus is situated at the upper part of the lateral side of the leg, and is the more superficial of the two muscles. It arises from the head and upper two-thirds of the lateral surface of the body of the fibula, from the deep surface of the fascia, and from the intermuscular septa between it and the muscles on the front and back of the leg; occasionally also by a few fibers from the lateral condyle of the tibia. Between its attachments to the head and to the body of the fibula there is a gap through which the common peroneal nerve passes to the front of the leg. It ends in a long tendon, which runs behind the lateral malleolus, in a groove common to it and the tendon of the Peronæus brevis, behind which it lies; the groove is converted into a canal by the superior peroneal retinaculum, and the tendons in it are contained in a common mucous sheath. The tendon then extends obliquely forward across the lateral side of the calcaneus, below the trochlear process, and the tendon of the Peronæus brevis, and under cover of the inferior peroneal retinaculum. It crosses the lateral side of the cuboid, and then runs on the under surface of that bone in a groove which is converted into a canal by the long plantar ligament; the tendon then crosses the sole of the foot obliquely, and is inserted into the lateral side of the base of the first metatarsal bone and the lateral side of the first cuneiform. Occasionally it sends a slip to the base of the second metatarsal bone. The tendon changes its direction at two points: first, behind the lateral malleolus; secondly, on the cuboid bone; in both of these situations the tendon is thickened, and, in the latter, a sesamoid fibrocartilage (sometimes a bone), is usually developed in its substance.
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FIG. 440– Cross-section through middle of leg. (Eycleshymer and Schoemaker.) (See enlarged image)



The Peronæus brevis lies under cover of the Peronæus longus, and is a shorter and smaller muscle. It arises from the lower two-thirds of the lateral surface of the body of the fibula; medial to the Peronæus longus; and from the intermuscular septa separating it from the adjacent muscles on the front and back of the leg. The fibers pass vertically downward, and end in a tendon which runs behind the lateral malleolus along with but in front of that of the preceding muscle, the two tendons being enclosed in the same compartment, and lubricated by a common mucous sheath. It then runs forward on the lateral side of the calcaneus, above the trochlear process and the tendon of the Peronæus longus, and is inserted into the tuberosity at the base of the fifth metatarsal bone, on its lateral side.
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On the lateral surface of the calcaneus the tendons of the Peronæi longus and brevis occupy separate osseoaponeurotic canals formed by the calcaneus and the perineal retinacula; each tendon is enveloped by a forward prolongation of the common mucous sheath.
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Variations.—Fusion of the two peronæi is rare. A slip from the Peronæus longus to the base of the third, fourth or fifth metatarsal bone, or to the Adductor hallucis is occasionally seen.
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Peronæus accessorius, origin from the fibula between the longus and brevis, joins the tendon of the longus in the sole of the foot.
36

Peronæus quinti digiti, rare, origin lower fourth of the fibula under the brevis, insertion into the Extensor aponeurosis of the little toe. More common as a slip of the tendon of the Peronæus brevis.
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Peronæus quartus, 13 per cent. (Gruber), origin back of fibula between the brevis and the Flexor hallucis, insertion into the peroneal spine of the calcaneum, (peroneocalcaneus externum), or less frequently into the tuberosity of the cuboid (peroneocuboideus).
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Nerves.—The Peronæi longus and brevis are supplied by the fourth and fifth lumbar and first sacral nerves through the superficial peroneal nerve.
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Actions.—The Peronæi longus and brevis extend the foot upon the leg, in conjunction with the Tibialis posterior, antagonizing the Tibialis anterior and Peronæus tertius, which are flexors of the foot. The Peronæus longus also everts the sole of the foot, and from the oblique direction of the tendon across the sole of the foot is an important agent in the maintenance of the transverse arch. Taking their fixed points below, the Peronæi serve to steady the leg upon the foot. This is especially the case in standing upon one leg, when the tendency of the superincumbent weight is to throw the leg medialward; the Peronæus longus overcomes this tendency by drawing on the lateral side of the leg.
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the foot



8e. The Muscles and Fasciæ of the Foot





1. [b]The Dorsal Muscle of the Foot[/b]



Extensor digitorum brevis—The fascia on the dorsum of the foot is a thin membranous layer, continuous above with the transverse and cruciate crural ligaments; on either side it blends with the plantar aponeurosis; anteriorly it forms a sheath for the tendons on the dorsum of the foot.
1



The Extensor digitorum brevis (Fig. 441) is a broad, thin muscle, which arises from the forepart of the upper and lateral surfaces of the calcaneus, in front of the groove for the Peronæus brevis; from the lateral talocalcanean ligament; and from the common limb of the cruciate crural ligament. It passes obliquely across the dorsum of the foot, and ends in four tendons. The most medial, which is the largest, is inserted into the dorsal surface of the base of the first phalanx of the great toe, crossing the dorsalis pedis artery; it is frequently described as a separate muscle—the Extensor hallucis brevis. The other three are inserted into the lateral sides of the tendons of the Extensor digitorum longus of the second, third, and fourth toes.
2



Variations.—Accessory slips of origin from the talus and navicular, or from the external cunei-form and third metatarsal bones to the second slip of the muscle, and one from the cuboid to the third slip have been observed. The tendons vary in number and position; they may be reduced to two, or one of them may be doubled, or an additional slip may pass to the little toe. A supernumerary slip ending on one of the metatarsophalangeal articulations, or joining a dorsal interosseous muscle is not uncommon. Deep slips between this muscle and the Dorsal interossei occur.
3



Nerves.—It is supplied by the deep peroneal nerve.
4



Actions.—The Extensor digitorum brevis extends the phalanges of the four toes into which it is inserted, but in the great toe acts only on the first phalanx. The obliquity of its direction counteracts the oblique movement given to the toes by the long Extensor, so that when both muscles act, the toes are evenly extended.
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2. [b]The Plantar Muscles of the Foot[/b]



Plantar Aponeurosis (aponeurosis plantaris; plantar fascia).—The plantar aponeurosis is of great strength, and consists of pearly white glistening fibers, disposed, for the most part, longitudinally: it is divided into central, lateral, and medial portions.
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The central portion, the thickest, is narrow behind and attached to the medial process of the tuberosity of the calcaneus, posterior to the origin of the Flexor digitorum brevis; and becoming broader and thinner in front, divides near the heads of the metatarsal bones into five processes, one for each of the toes. Each of these processes divides opposite the metatarsophalangeal articulation into two strata, superficial and deep. The superficial stratum is inserted into the skin of the transverse sulcus which separates the toes from the sole. The deeper stratum divides into two slips which embrace the side of the Flexor tendons of the toes, and blend with the sheaths of the tendons, and with the transverse metatarsal ligament, thus forming a series of arches through which the tendons of the short and long Flexors pass to the toes. The intervals left between the five processes allow the digital vessels and nerves and the tendons of the Lumbricales to become superficial. At the point of division of the aponeurosis, numerous transverse fasciculi are superadded; these serve to increase the strength of the aponeurosis at this part by binding the processes together, and connecting them with the integument. The central portion of the plantar aponeurosis is continuous with the lateral and medial portions and sends upward into the foot, at the lines of junction, two strong vertical intermuscular septa, broader in front than behind, which separate the intermediate from the lateral and medial plantar groups of muscles; from these again are derived thinner transverse septa which separate the various layers of muscles in this region. The upper surface of this aponeurosis gives origin behind to the Flexor digitorum brevis.
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The lateral and medial portions of the plantar aponeurosis are thinner than the central piece, and cover the sides of the sole of the foot.
8

The lateral portion covers the under surface of the Abductor digiti quinti; it is thin in front and thick behind, where it forms a strong band between the lateral process of the tuberosity of the calcaneus and the base of the fifth metatarsal bone; it is continuous medially with the central portion of the plantar aponeurosis, and laterally with the dorsal fascia.
9

The medial portion is thin, and covers the under surface of the Abductor hallucis; it is attached behind to the laciniate ligament, and is continuous around the side of the foot with the dorsal fascia, and laterally with the central portion of the plantar aponeurosis.
10

The muscles in the plantar region of the foot may be divided into three groups, in a similar manner to those in the hand. Those of the medial plantar region are connected with the great toe, and corrrespond with those of the thumb; those of the lateral plantar region are connected with the little toe, and correspond with those of the little finger; and those of the intermediate plantar region are connected with the tendons intervening between the two former groups. But in order to facilitate the description of these muscles, it is more convenient to divide them into four layers, in the order in which they are successively exposed.
11



[b]The First Layer (Fig. 443).[/b]





Abductor hallucis.


Flexor digitorum brevis.

Abductor digiti quinti.

The Abductor hallucis lies along the medial border of the foot and covers the origins of the plantar vessels and nerves. It arises from the medial process of the tuberosity of the calcaneus, from the laciniate ligament, from the plantar aponeurosis, and from the intermuscular septum between it and the Flexor digitorum brevis. The fibers end in a tendon, which is inserted, together with the medial tendon of the Flexor hallucis brevis, into the tibial side of the base of the first phalanx of the great toe.
12



Variations.—Slip to the base of the first phalanx of the second toe.
13

The Flexor digitorum brevis lies in the middle of the sole of the foot, immediately above the central part of the plantar aponeurosis, with which it is firmly united. Its deep surface is separated from the lateral plantar vessels and nerves by a thin layer of fascia. It arises by a narrow tendon, from the medial process of the tuberosity of the calcaneus, from the central part of the plantar aponeurosis, and from the intermuscular septa between it and the adjacent muscles. It passes forward, and divides into four tendons, one for each of the four lesser toes. Opposite the bases of the first phalanges, each tendon divides into two slips, to allow of the passage of the corresponding tendon of the Flexor digitorum longus; the two portions of the tendon then unite and form a grooved channel for the reception of the accompanying long Flexor tendon. Finally, it divides a second time, and is inserted into the sides of the second phalanx about its middle. The mode of division of the tendons of the Flexor digitorum brevis, and of their insertion into the phalanges, is analogous to that of the tendons of the Flexor digitorum sublimis in the hand.
14



Variations.—Slip to the little toe frequently wanting, 23 per cent.; or it may be replaced by a small fusiform muscle arising from the long flexor tendon or from the Quadratus plantæ.
15



Fibrous Sheaths of the Flexor Tendons.—The terminal portions of the tendons of the long and short Flexor muscles are contained in osseoaponeurotic canals similar in their arrangement to those in the fingers. These canals are formed above by the phalanges and below by fibrous bands, which arch across the tendons, and are attached on either side to the margins of the phalanges. Opposite the bodies of the proximal and second phalanges the fibrous bands are strong, and the fibers are transverse; but opposite the joints they are much thinner, and the fibers are directed obliquely. Each canal contains a mucous sheath, which is reflected on the contained tendons.
16





FIG. 443– Muscles of the sole of the foot. First layer. (See enlarged image)



The Abductor digiti quinti (Abductor minimi digiti) lies along the lateral border of the foot, and is in relation by its medial margin with the lateral plantar vessels and nerves. It arises, by a broad origin, from the lateral process of the tuberosity of the calcaneus, from the under surface of the calcaneus between the two processes of the tuberosity, from the forepart of the medial process, from the plantar aponeurosis, and from the intermuscular septum between it and the Flexor digitorum brevis. Its tendon, after gliding over a smooth facet on the under surface of the base of the fifth metatarsal bone, is inserted, with the Flexor digiti quinti brevis, into the fibular side of the base of the first phalanx of the fifth toe.
17



Variations.—Slips of origin from the tuberosity at the base of the fifth metatarsal. Abductor ossis metatarsi quinti, origin external tubercle of the calcaneus, insertion into tuberosity of the fifth metatarsal bone in common with or beneath the outer margin of the plantar fascia.
18



[b]The Second Layer (Fig. 444).[/b]





Quadratus plantæ.


Lumbricales.

The Quadratus plantæ (Flexor accessorius) is separated from the muscles of the first layer by the lateral plantar vessels and nerve. It arises by two heads, which are separated from each other by the long plantar ligament: the medial or larger head is muscular, and is attached to the medial concave surface of the calcaneus, below the groove which lodges the tendon of the Flexor hallucis longus; the lateral head, flat and tendinous, arises from the lateral border of the inferior surface of the calcaneus, in front of the lateral process of its tuberosity, and from the long plantar ligament. The two portions join at an acute angle, and end in a flattened band which is inserted into the lateral margin and upper and under surfaces of the tendon of the Flexor digitorum longus, forming a kind of groove, in which the tendon is lodged. It usually sends slips to those tendons of the Flexor digitorum longus which pass to the second, third, and fourth toes.
19



Variations.—Lateral head often wanting; entire muscle absent. Variation in the number of digital tendons to which fibers can be traced. Most frequent offsets are sent to the second, third and fourth toes; in many cases to the fifth as well; occasionally to two toes only.
20

The Lumbricales are four small muscles, accessory to the tendons of the Flexor digitorum longus and numbered from the medial side of the foot; they arise from these tendons, as far back as their angles of division, each springing from two tendons, except the first. The muscles end in tendons, which pass forward on the medial sides of the four lesser toes, and are inserted into the expansions of the tendons of the Extensor digitorum longus on the dorsal surfaces of the first phalanges.
21



Variations.—Absence of one or more; doubling of the third or fourth. Insertion partly or wholly into the first phalanges.
22

[b]The Third Layer (Fig. 445).[/b]





Flexor hallucis brevis.


Adductor hallucis.

Flexor digiti quinti brevis.

The Flexor hallucis brevis arises, by a pointed tendinous process, from the medial part of the under surface of the cuboid bone, from the contiguous portion of the third cuneiform, and from the prolongation of the tendon of the Tibialis posterior which is attached to that bone. It divides in front into two portions, which are inserted into the medial and lateral sides of the base of the first phalanx of the great toe, a sesamoid bone being present in each tendon at its insertion. The medial portion is blended with the Abductor hallucis previous to its insertion; the lateral portion with the Adductor hallucis; the tendon of the Flexor hallucis longus lies in a groove between them; the lateral portion is sometimes described as the first Interosseous plantaris.
23



Variations.—Origin subject to considerable variation; it often receives fibers from the calcaneus or long plantar ligament. Attachment to the cuboid sometimes wanting. Slip to first phalanx of the second toe.
24

The Adductor hallucis (Adductor obliquus hallucis) arises by two heads—oblique and transverse. The oblique head is a large, thick, fleshy mass, crossing the foot obliquely and occupying the hollow space under the first second, third, and fourth metatarsal bones. It arises from the bases of the second, third, and fourth metatarsal bones, and from the sheath of the tendon of the Peronæus longus, and is inserted, together with the lateral portion of the Flexor hallucis brevis, into the lateral side of the base of the first phalanx of the great toe. The transverse head (Transversus pedis) is a narrow, flat fasciculus which arises from the plantar metatarsophalangeal ligaments of the third, fourth, and fifth toes (sometimes only from the third and fourth), and from the transverse ligament of the metatarsus. It is inserted into the lateral side of the base of the first phalanx of the great toe, its fibers blending with the tendon of insertion of the oblique head.
25




FIG. 444– Muscles of the sole of the foot. Second layer. (See enlarged image)






FIG. 445– Muscles of the sole of the foot. Third layer. (See enlarged image)





Variations.—Slips to the base of the first phalanx of the second toe. Opponens hallucis, occasional slips from the adductor to the metatarsal bone of the great toe.
26

The Abductor, Flexor brevis, and Adductor of the great toe, like the similar muscles of the thumb, give off, at their insertions, fibrous expansions to blend with the tendons of the Extensor digitorum longus.
27

The Flexor digiti quinti brevis (Flexor brevis minimi digiti) lies under the metatarsal bone of the little toe, and resembles one of the Interossei. It arises from the base of the fifth metatarsal bone, and from the sheath of the Peronæus longus; its tendon is inserted into the lateral side of the base of the first phalanx of the fifth toe. Occasionally a few of the deeper fibers are inserted into the lateral part of the distal half of the fifth metatarsal bone; these are described by some as a distinct muscle, the Opponens digiti quinti.
28



The Fourth Layer



Interossei—The Interossei in the foot are similar to those in the hand, with this exception, that they are grouped around the middle line of the second digit, instead of that of the third. They are seven in number, and consist of two groups, dorsal and plantar.
29

The Interossei dorsales (Dorsal interossei) (Fig. 446), four in number, are situated between the metatarsal bones. They are bipenniform muscles, each arising by two heads from the adjacent sides of the metatarsal bones between which it is placed; their tendons are inserted into the bases of the first phalanges, and into the aponeurosis of the tendons of the Extensor digitorum longus. In the angular interval left between the heads of each of the three lateral muscles, one of the perforating arteries passes to the dorsum of the foot; through the space between the heads of the first muscle the deep plantar branch of the dorsalis pedis artery enters the sole of the foot. The first is inserted into the medial side of the second toe; the other three are inserted into the lateral sides of the second, third, and fourth toes.
30




FIG. 446– The Interossei dorsales. Left foot. (See enlarged image)






FIG. 447– The Interossei plantares. Left foot. (See enlarged image)



The Interossei plantares (Plantar interossei) (Fig. 447), three in number, lie beneath rather than between the metatarsal bones, and each is connected with but one metatarsal bone. They arise from the bases and medial sides of the bodies of the third, fourth, and fifth metatarsal bones, and are inserted into the medial sides of the bases of the first phalanges of the same toes, and into the aponeuroses of the tendons of the Extensor digitorum longus.
31



Nerves.—The Flexor digitorum brevis, the Flexor hallucis brevis, the Abductor hallucis, and the first Lumbricalis are supplied by the medial plantar nerve; all the other muscles in the sole of the foot by the lateral plantar. The first Interosseous dorsalis frequently receives an extra filament from the medial branch of the deep peroneal nerve on the dorsum of the foot, and the second Interosseous dorsalis a twig from the lateral branch of the same nerve.
32



Actions.—All the muscles of the foot act upon the toes, and may be grouped as abductors, adductors, flexors, or extensors. The abductors are the Interossei dorsales, the Abductor hallucis, and the Abductor digiti quinti. The Interossei dorsales are abductors from an imaginary line passing through the axis of the second toe, so that the first muscle draws the second toe medialward, toward the great toe, the second muscle draws the same toe lateralward, and the third and fourth draw the third and fourth toes in the same direction. Like the Interossei in the hand, each assists in flexing the first phalanx and extending the second and third phalanges. The Abductor hallucis abducts the great toe from the second, and also flexes its proximal phalanx. In the same way the action of the Abductor digiti quinti is twofold, as an abductor of this toe from the fourth, and also as a flexor of its proximal phalanx. The adductors are the Interossei plantares and the Adductor hallucis. The Interossei plantares adduct the third, fourth, and fifth toes toward the imaginary line passing through the second toe, and by means of their insertions into the aponeuroses of the Extensor tendons they assist in flexing the proximal phalanges and extending the middle and terminal phalanges. The oblique head of the Adductor hallucis is chiefly concerned in adducting the great toe toward the second one, but also assists in flexing this toe; the transverse head approximates all the toes and thus increases the curve of the transverse arch of the metatarsus. The flexors are the Flexor digitorum brevis, the Quadratus plantæ, the Flexor hallucis brevis, the Flexor digiti quinti brevis, and the Lumbricales. The Flexor digitorum brevis flexes the second phalanges upon the first, and, continuing its action, flexes the first phalanges also, and brings the toes together. The Quadratus plantæ assists the Flexor digitorum longus and converts the oblique pull of the tendons of that muscle into a direct backward pull upon the toes. The Flexor digiti quinti brevis flexes the little toe and draws its metatarsal bone downward and medialward. The Lumbricales, like the corresponding muscles in the hand, assist in flexing the proximal phalanges, and by their insertions into the tendons of the Extensor digitorum longus aid that muscle in straightening the middle and terminal phalanges. The Extensor digitorum brevis extends the first phalanx of the great toe and assists the long Extensor in extending the next three toes, and at the same time gives to the toes a lateral direction when they are extended.
33

the thigh





8b. The Muscles and Fasciæ of the Thigh





1. [b]The Anterior Femoral Muscles (Fig. 430).[/b]





Sartorius.
Quadriceps
femoris.
Rectus femoris.

Vastus lateralis.

Vastus medialis.

Vastus intermedius.

Articularis genu.



Superficial Fascia.—The superficial fascia forms a continuous layer over the whole of the thigh; it consists of areolar tissue containing in its meshes much fat, and may be separated into two or more layers, between which are found the superficial vessels and nerves. It varies in thickness in different parts of the limb; in the groin it is thick, and the two layers are separated from one another by the superficial inguinal lymph glands, the great saphenous vein, and several smaller vessels. The superficial layer is continuous above with the superficial fascia of the abdomen. The deep layer of the superficial fascia is a very thin, fibrous stratum, best marked on the medial side of the great saphenous vein and below the inguinal ligament. It is placed beneath the subcutaneous vessels and nerves and upon the surface of the fascia lata. It is intimately adherent to the fascia lata a little below the inguinal ligament. It covers the fossa ovalis (saphenous opening), being closely united to its circumference, and is connected to the sheath of the femoral vessels. The portion of fascia covering this fossa is perforated by the great saphenous vein and by numerous blood and lymphatic vessels, hence it has been termed the fascia cribrosa, the openings for these vessels having been likened to the holes in a sieve. A large subcutaneous bursa is found in the superficial fascia over the patella.
1



Deep Fascia.—The deep fascia of the thigh is named, from its great extent, the fascia lata; it constitutes an investment for the whole of this region of the limb, but varies in thickness in different parts. Thus, it is thicker in the upper and lateral part of the thigh, where it receives a fibrous expansion from the Glutæus maximus, and where the Tensor fasciæ latæ is inserted between its layers; it is very thin behind and at the upper and medial part, where it covers the Adductor muscles, and again becomes stronger around the knee, receiving fibrous expansions from the tendon of the Biceps femoris laterally, from the Sartorius medially, and from the Quadriceps femoris in front. The fascia lata is attached, above and behind, to the back of the sacrum and coccyx; laterally, to the iliac crest; in front, to the inguinal ligament, and to the superior ramus of the pubis; and medially, to the inferior ramus of the pubis, to the inferior ramus and tuberosity of the ischium, and to the lower border of the sacrotuberous ligament. From its attachment to the iliac crest it passes down over the Glutæus medius to the upper border of the Glutæus maximus, where it splits into two layers, one passing superficial to and the other beneath this muscle; at the lower border of the muscle the two layers reunite. Laterally, the fascia lata receives the greater part of the tendon of insertion of the Glutæus maximus, and becomes proportionately thickened. The portion of the fascia lata attached to the front part of the iliac crest, and corresponding to the origin of the Tensor fasciæ latæ, extends down the lateral side of the thigh as two layers, one superficial to and the other beneath this muscle; at the lower end of the muscle these two layers unite and form a strong band, having first received the insertion of the muscle. This band is continued downward, under the name of the iliotibial band (tractus iliotibialis) and is attached to the lateral condyle of the tibia. The part of the iliotibial band which lies beneath the Tensor fasciæ latæ is prolonged upward to join the lateral part of the capsule of the hip-joint. Below, the fasciæ lata is attached to all the prominent points around the knee-joint, viz., the condyles of the femur and tibia, and the head of the fibula. On either side of the patella it is strengthened by transverse fibers from the lower parts of the Vasti, which are attached to and support this bone. Of these the lateral are the stronger, and are continuous with the iliotibial band. The deep surface of the fascia lata gives off two strong intermuscular septa, which are attached to the whole length of the linea aspera and its prolongations above and below; the lateral and stronger one, which extends from the insertion of the Glutæus maximus to the lateral condyle, separates the Vastus lateralis in front from the short head of the Biceps femoris behind, and gives partial origin to these muscles; the medial and thinner one separates the Vastus medialis from the Adductores and Pectineus. Besides these there are numerous smaller septa, separating the individual muscles, and enclosing each in a distinct sheath.
2



The Fossa Ovalis (saphenous opening) (Fig. 431).—At the upper and medial part of the thigh, a little below the medial end of the inguinal ligament, is a large oval-shaped aperture in the fascia lata; it transmits the great saphenous vein, and other, smaller vessels, and is termed the fossa ovalis. The fascia cribrosa, which is pierced by the structures passing through the opening, closes the aperture and must be removed to expose it. The fascia lata in this part of the thigh is described as consisting of a superficial and a deep portion.
3





FIG. 431– The fossa ovalis. (See enlarged image)





The superficial portion of the fascia lata is the part on the lateral side of the fossa ovalis. It is attached, laterally, to the crest and anterior superior spine of the ilium, to the whole length of the inguinal ligament, and to the pectineal line in conjunction with the lacunar ligament. From the tubercle of the pubis it is reflected downward and lateralward, as an arched margin, the falciform margin, forming the lateral boundary of the fossa ovalis; this margin overlies and is adherent to the anterior layer of the sheath of the femoral vessels: to its edge is attached the fascia cribrosa. The upward and medial prolongation of the falciform margin is named the superior cornu; its downward and medial prolongation, the inferior cornu. The latter is well-defined, and is continuous behind the great saphenous vein with the pectineal fascia.
4

The deep portion is situated on the medial side of the fossa ovalis, and at the lower margin of the fossa is continuous with the superficial portion; traced upward, it covers the Pectineus, Adductor longus, and Gracilis, and, passing behind the sheath of the femoral vessels, to which it is closely united, is continuous with the iliopectineal fascia, and is attached to the pectineal line.
5

From this description it may be observed that the superficial portion of the fascia lata lies in front of the femoral vessels, and the deep portion behind them, so that an apparent aperture exists between the two, through which the great saphenous passes to join the femoral vein.
6

The Sartorius, the longest muscle in the body, is narrow and ribbon-like; it arises by tendinous fibers from the anterior superior iliac spine and the upper half of the notch below it. It passes obliquely across the upper and anterior part of the thigh, from the lateral to the medial side of the limb, then descends vertically, as far as the medial side of the knee, passing behind the medial condyle of the femur to end in a tendon. This curves obliquely forward and expands into a broad aponeurosis, which is inserted, in front of the Gracilis and Semitendinous, into the upper part of the medial surface of the body of the tibia, nearly as far forward as the anterior crest. The upper part of the aponeurosis is curved backward over the upper edge of the tendon of the Gracilis so as to be inserted behind it. An offset, from its upper margin, blends with the capsule of the knee-joint, and another from its lower border, with the fascia on the medial side of the leg.
7



Variations.—Slips of origin from the outer end of the inguinal ligament, the notch of the ilium, the ilio-pectineal line or the pubis occur. The muscle may be split into two parts, and one part may be inserted into the fascia lata, the femur, the ligament of the patella or the tendon of the Semitendinosus. The tendon of insertion may end in the fascia lata, the capsule of the knee-joint, or the fascia of the leg. The muscle may be absent.
8

The Quadriceps femoris (Quadriceps extensor) includes the four remaining muscles on the front of the thigh. It is the great extensor muscle of the leg, forming a large fleshy mass which covers the front and sides of the femur. It is subdivided into separate portions, which have received distinctive names. One occupying the middle of the thigh, and connected above with the ilium, is called from its straight course the Rectus femoris. The other three lie in immediate connection with the body of the femur, which they cover from the trochanters to the condyles. The portion on the lateral side of the femur is termed the Vastus lateralis; that covering the medial side, the Vastus medialis; and that in front, the Vastus intermedius.
9

The Rectus femoris is situated in the middle of the front of the thigh; it is fusiform in shape, and its superficial fibers are arranged in a bipenniform manner, the deep fibers running straight down to the deep aponeurosis. It arises by two tendons: one, the anterior or straight, from the anterior inferior iliac spine; the other, the posterior or reflected, from a groove above the brim of the acetabulum. The two unite at an acute angle, and spread into an aponeurosis which is prolonged downward on the anterior surface of the muscle, and from this the muscular fibers arise. The muscle ends in a broad and thick aponeurosis which occupies the lower two-thirds of its posterior surface, and, gradually becoming narrowed into a flattened tendon, is inserted into the base of the patella.
10

The Vastus lateralis (Vastus externus) is the largest part of the Quadriceps femoris. It arises by a broad aponeurosis, which is attached to the upper part of the intertrochanteric line, to the anterior and inferior borders of the greater trochanter, to the lateral lip of the gluteal tuberosity, and to the upper half of the lateral lip of the linea aspera; this aponeurosis covers the upper three-fourths of the muscle, and from its deep surface many fibers take origin. A few additional fibers arise from the tendon of the Glutæus maximus, and from the lateral intermuscular septum between the Vastus lateralis and short head of the Biceps femoris. The fibers form a large fleshy mass, which is attached to a strong aponeurosis, placed on the deep surface of the lower part of the muscle: this aponeurosis becomes contracted and thickened into a flat tendon inserted into the lateral border of the patella, blending with the Quadriceps femoris tendon, and giving an expansion to the capsule of the knee-joint.
11

The Vastus medialis and Vastus intermedius appear to be inseparably united, but when the Rectus femoris has been reflected a narrow interval will be observed extending upward from the medial border of the patella between the two muscles, and the separation may be continued as far as the lower part of the intertrochanteric line, where, however, the two muscles are frequently continuous.
12

The Vastus medialis (Vastus internus) arises from the lower half of the intertrochanteric line, the medial lip of the linea aspera, the upper part of the medial supracondylar line, the tendons of the Adductor longus and the Adductor magnus and the medial intermuscular septum. Its fibers are directed downward and forward, and are chiefly attached to an aponeurosis which lies on the deep surface of the muscle and is inserted into the medial border of the patella and the Quadriceps femoris tendon, an expansion being sent to the capsule of the knee-joint.
13

The Vastus intermedius (Crureus) arises from the front and lateral surfaces of the body of the femur in its upper two-thirds and from the lower part of the lateral intermuscular septum. Its fibers end in a superficial aponeurosis, which forms the deep part of the Quadriceps femoris tendon.
14

The tendons of the different portions of the Quadriceps unite at the lower part of the thigh, so as to form a single strong tendon, which is inserted into the base of the patella, some few fibers passing over it to blend with the ligamentum patellæ. More properly, the patella may be regarded as a sesamoid bone, developed in the tendon of the Quadriceps; and the ligamentum patellæ, which is continued from the apex of the patella to the tuberosity of the tibia, as the proper tendon of insertion of the muscle, the medial and lateral patellar retinacula (see p. 338) being expansions from its borders. A bursa, which usually communicates with the cavity of the knee-joint, is situated between the femur and the portion of the Quadriceps tendon above the patella; another is interposed between the tendon and the upper part of the front of the tibia; and a third, the prepatellar bursa, is placed over the patella itself.
15

The Articularis genu (Subcrureus) is a small muscle, usually distinct from the Vastus intermedius, but occasionally blended with it; it arises from the anterior surface of the lower part of the body of the femur, and is inserted into the upper part of the synovial membrane of the knee-joint. It sometimes consists of several separate muscular bundles.
16



Nerves.—The muscles of this region are supplied by the second, third, and fourth lumbar nerves, through the femoral nerve.
17



Actions.—The Sartorius flexes the leg upon the thigh, and, continuing to act, flexes the thigh upon the pelvis; it next abducts and rotates the thigh outward. When the knee is bent, the Sartorius assists the Semitendinosus, Semimembranosus, and Popliteus in rotating the tibia inward. Taking its fixed point from the leg, it flexes the pelvis upon the thigh, and, if one muscle acts, assists in rotating the pelvis. The Quadriceps femoris extends the leg upon the thigh. The Rectus femoris assists the Psoas major and Iliacus in supporting the pelvis and trunk upon the femur. It also assists in flexing the thigh on the pelvis, or if the thigh be fixed it will flex the pelvis. The Vastus medialis draws the patella medialward as well as upward.
18

[b]2. [b]The Medial Femoral Muscles[/b]





Gracilis.
Adductor longus.
Adductor magnus.

Pectineus.
Adductor brevis.

The Gracilis (Fig. 430) is the most superficial muscle on the medial side of the thigh. It is thin and flattened, broad above, narrow and tapering below. It arises by a thin aponeurosis from the anterior margins of the lower half of the symphysis pubis and the upper half of the pubic arch. The fibers run vertically downward, and end in a rounded tendon, which passes behind the medial condyle of the femur, curves around the medial condyle of the tibia, where it becomes flattened, and is inserted into the upper part of the medial surface of the body of the tibia, below the condyle. A few of the fibers of the lower part of the tendon are prolonged into the deep fascia of the leg. At its insertion the tendon is situated immediately above that of the Semitendinosus, and its upper edge is overlapped by the tendon of the Sartorius, with which it is in part blended. It is separated from the tibial collateral ligament of the knee-joint, by a bursa common to it and the tendon of the Semitendinosus.
19





FIG. 432– Cross-section through the middle of the thigh. (Eycleshymer and Schoemaker.) (See enlarged image)



The Pectineus (Fig. 430) is a flat, quadrangular muscle, situated at the anterior part of the upper and medial aspect of the thigh. It arises from the pectineal line, and to a slight extent from the surface of bone in front of it, between the iliopectineal eminence and tubercle of the pubis, and from the fascia covering the anterior surface of the muscle; the fibers pass downward, backward, and lateralward, to be inserted into a rough line leading from the lesser trochanter to the linea aspera.
20

The Adductor longus (Fig. 433), the most superficial of the three Adductores, is a triangular muscle, lying in the same plane as the Pectineus. It arises by a flat, narrow tendon, from the front of the pubis, at the angle of junction of the crest with the symphysis; and soon expands into a broad fleshy belly. This passes downward, backward, and lateralward, and is inserted, by an aponeurosis, into the linea aspera, between the Vastus medialis and the Adductor magnus, with both of which it is usually blended.
21

The Adductor brevis (Fig. 433) is situated immediately behind the two preceding muscles. It is somewhat triangular in form, and arises by a narrow origin from the outer surfaces of the superior and inferior rami of the pubis, between the Gracilis and Obturator externus. Its fibers, passing backward, lateralward, and downward, are inserted, by an aponeurosis, into the line leading from the lesser trochanter to the linea aspera and into the upper part of the linea aspera, immediately behind the Pectineus and upper part of the Adductor longus.
22

The Adductor magnus (Fig. 433) is a large triangular muscle, situated on the medial side of the thigh. It arises from a small part of the inferior ramus of the pubis, from the inferior ramus of the ischium, and from the outer margin of the inferior part of the tuberosity of the ischium. Those fibers which arise from the ramus of the pubis are short, horizontal in direction, and are inserted into the rough line leading from the greater trochanter to the linea aspera, medial to the Glutæus maximus; those from the ramus of the ischium are directed downward and lateralward with different degrees of obliquity, to be inserted, by means of a broad aponeurosis, into the linea aspera and the upper part of its medial prolongation below. The medial portion of the muscle, composed principally of the fibers arising from the tuberosity of the ischium, forms a thick fleshy mass consisting of coarse bundles which descend almost vertically, and end about the lower third of the thigh in a rounded tendon which is inserted into the adductor tubercle on the medial condyle of the femur, and is connected by a fibrous expansion to the line leading upward from the tubercle to the linea aspera. At the insertion of the muscle, there is a series of osseoaponeurotic openings, formed by tendinous arches attached to the bone. The upper four openings are small, and give passage to the perforating branches of the profunda femoris artery. The lowest is of large size, and transmits the femoral vessels to the popliteal fossa.
23






FIG. 433– Deep muscles of the medial femoral region. (See enlarged image)





Variations.—The Pectineus is sometimes divided into an outer part supplied by the femoral nerve and an inner part supplied by the obturator nerve. The muscle may be attached to or inserted into the capsule of the hip-joint. The Adductor longus may be double, may extend to the knee, or be more or less united with the Pectineus. The Adductor brevis may be divided into two or three parts, or it may be united to the Adductor magnus. The Adductor magnus may be more or less segmented, the anterior and superior portion is often described as a separate muscle, the Adductor minimus. The muscle may be fused with the Quadratus femoris.
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Nerves.—The three Adductores and the Gracilis are supplied by the third and fourth lumbar nerves through the obturator nerve; the Adductor magnus receiving an additional branch from the sacral plexus through the sciatic. The Pectineus is supplied by the second, third, and fourth lumbar nerves through the femoral nerve, and by the third lumbar through the accessory obturator when this latter exists. Occasionally it receives a branch from the obturator nerve. 86
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Actions.—The Pectineus and three Adductores adduct the thigh powerfully; they are especially used in horse exercise, the sides of the saddle being grasped between the knees by the contraction of these muscles. In consequence of the obliquity of their insertions into the linea aspera, they rotate the thigh outward, assisting the external Rotators, and when the limb has been abducted, they draw it medialward, carrying the thigh across that of the opposite side. The Pectineus and Adductores brevis and longus assist the Psoas major and Iliacus in flexing the thigh upon the pelvis. In progression, all these muscles assist in drawing forward the lower limb. The Gracilis assists the Sartorius in flexing the leg and rotating it inward; it is also an adductor of the thigh. If the lower extremities be fixed, these muscles, taking their fixed points below, may act upon the pelvis, serving to maintain the body in an erect posture; or, if their action be continued, flex the pelvis forward upon the femur.
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3. [b]The Muscles of the Gluteal Region (Fig. 434).[/b]





Glutæus maximus.


Obturator internus.

Glutæus medius.


Gemellus superior.

Glutæus minimus.


Gemellus inferior.

Tensor fasciæ latæ.


Quadratus femoris.

Piriformis.


Obturator externus.

The Glutæus maximus, the most superficial muscle in the gluteal region, is a broad and thick fleshy mass of a quadrilateral shape, and forms the prominence of the nates. Its large size is one of the most characteristic features of the muscular system in man, connected as it is with the power he has of maintaining the trunk in the erect posture. The muscle is remarkably coarse in structure, being made up of fasciculi lying parallel with one another and collected together into large bundles separated by fibrous septa. It arises from the posterior gluteal line of the ilium, and the rough portion of bone including the crest, immediately above and behind it; from the posterior surface of the lower part of the sacrum and the side of the coccyx; from the aponeurosis of the Sacrospinalis, the sacrotuberous ligament, and the fascia (gluteal aponeurosis) covering the Glutæus medius. The fibers are directed obliquely downward and lateralward; those forming the upper and larger portion of the muscle, together with the superficial fibers of the lower portion, end in a thick tendinous lamina, which passes across the greater trochanter, and is inserted into the iliotibial band of the fascia lata; the deeper fibers of the lower portion of the muscle are inserted into the gluteal tuberosity between the Vastus lateralis and Adductor magnus.
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Bursæ—Three bursæ are usually found in relation with the deep surface of this muscle. One of these, of large size, and generally multilocular, separates it from the greater trochanter; a second, often wanting, is situated on the tuberosity of the ischium; a third is found between the tendon of the muscle and that of the Vastus lateralis.
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The Glutæus medius is a broad, thick, radiating muscle, situated on the outer surface of the pelvis. Its posterior third is covered by the Glutæus maximus, its anterior two-thirds by the gluteal aponeurosis, which separates it from the superficial fascia and integument. It arises from the outer surface of the ilium between the iliac crest and posterior gluteal line above, and the anterior gluteal line below; it also arises from the gluteal aponeurosis covering its outer surface. The fibers converge to a strong flattened tendon, which is inserted into the oblique ridge which runs downward and forward on the lateral surface of the greater trochanter. A bursa separates the tendon of the muscle from the surface of the trochanter over which it glides.
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Variations.—The posterior border may be more or less closely united to the Piriformis, or some of the fibers end on its tendon.
30

The Glutæus minimus, the smallest of the three Glutæi, is placed immediately beneath the preceding. It is fan-shaped, arising from the outer surface of the ilium, between the anterior and inferior gluteal lines, and behind, from the margin of the greater sciatic notch. The fibers converge to the deep surface of a radiated aponeurosis, and this ends in a tendon which is inserted into an impression on the anterior border of the greater trochanter, and gives an expansion to the capsule of the hip-joint. A bursa is interposed between the tendon and the greater trochanter. Between the Glutæus medius and Glutæus minimus are the deep branches of the superior gluteal vessels and the superior gluteal nerve. The deep surface of the Glutæus minimus is in relation with the reflected tendon of the Rectus femoris and the capsule of the hip-joint.
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Variations.—The muscle may be divided into an anterior and a posterior part, or it may send slips to the Piriformis, the Gemellus superior or the outer part of the origin of the Vastus lateralis.
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FIG. 434– Muscles of the gluteal and posterior femoral regions. (See enlarged image)



The Tensor fasciæ latæ (Tensor fasciæ femoris) arises from the anterior part of the outer lip of the iliac crest; from the outer surface of the anterior superior iliac spine, and part of the outer border of the notch below it, between the Glutæus medius and Sartorius; and from the deep surface of the fascia lata. It is inserted between the two layers of the iliotibial band of the fascia lata about the junction of the middle and upper thirds of the thigh.
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The Piriformis is a flat muscle, pyramidal in shape, lying almost parallel with the posterior margin of the Glutæus medius. It is situated partly within the pelvis against its posterior wall, and partly at the back of the hip-joint. It arises from the front of the sacrum by three fleshy digitations, attached to the portions of bone between the first, second, third, and fourth anterior sacral foramina, and to the grooves leading from the foramina: a few fibers also arise from the margin of the greater sciatic foramen, and from the anterior surface of the sacrotuberous ligament. The muscle passes out of the pelvis through the greater sciatic foramen, the upper part of which it fills, and is inserted by a rounded tendon into the upper border of the greater trochanter behind, but often partly blended with, the common tendon of the Obturator internus and Gemelli.
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Variations.—It is frequently pierced by the common peroneal nerve and thus divided more or less into two parts. It may be united with the Glutæus medius, or send fibers to the Glutæus minimus or receive fibers from the Gemellus superior. It may have only one or two sacral attachments or be inserted in to the capsule of the hip-joint. It may be absent.
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[/b]outward.

FIG. 435– The obturator membrane. (See enlarged image)





Obturator Membrane (Fig. 435).—The obturator membrane is a thin fibrous sheet, which almost completely closes the obturator foramen. Its fibers are arranged in interlacing bundles mainly transverse in direction; the uppermost bundle is attached to the obturator tubercles and completes the obturator canal for the passage of the obturator vessels and nerve. The membrane is attached to the sharp margin of the obturator foramen except at its lower lateral angle, where it is fixed to the pelvic surface of the inferior ramus of the ischium, i. e., within the margin. Both obturator muscles are connected with this membrane.
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The Obturator internus is situated partly within the lesser pelvis, and partly at the back of the hip-joint. It arises from the inner surface of the antero-lateral wall of the pelvis, where it surrounds the greater part of the obturator foramen, being attached to the inferior rami of the pubis and ischium, and at the side to the inner surface of the hip bone below and behind the pelvic brim, reaching from the upper part of the greater sciatic foramen above and behind to the obturator foramen below and in front. It also arises from the pelvic surface of the obturator membrane except in the posterior part, from the tendinous arch which completes the canal for the passage of the obturator vessels and nerve, and to a slight extent from the obturator fascia, which covers the muscle. The fibers converge rapidly toward the lesser sciatic foramen, and end in four or five tendinous bands, which are found on the deep surface of the muscle; these bands are reflected at a right angle over the grooved surface of the ischium between its spine and tuberosity. This bony surface is covered by smooth cartilage, which is separated from the tendon by a bursa, and presents one or more ridges corresponding with the furrows between the tendinous bands. These bands leave the pelvis through the lesser sciatic foramen and unite into a single flattened tendon, which passes horizontally across the capsule of the hip-joint, and, after receiving the attachments of the Gemelli, is inserted into the forepart of the medial surface of the greater trochanter above the trochanteric fossa. A bursa, narrow and elongated in form, is usually found between the tendon and the capsule of the hip-joint; it occasionally communicates with the bursa between the tendon and the ischium.
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The Gemelli are two small muscular fasciculi, accessories to the tendon of the Obturator internus which is received into a groove between them.
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The Gemellus superior, the smaller of the two, arises from the outer surface of the spine of the ischium, blends with the upper part of the tendon of the Obturator internus, and is inserted with it into the medial surface of the greater trochanter. It is sometimes wanting.
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The Gemellus inferior arises from the upper part of the tuberosity of the ischium, immediately below the groove for the Obturator internus tendon. It blends with the lower part of the tendon of the Obturator internus, and is inserted with it it into the medial surface of the greater trochanter. Rarely absent.
40

The Quadratus femoris is a flat, quadrilateral muscle, between the Gemellus inferior and the upper margin of the Adductor magnus; it is separated from the latter by the terminal branches of the medial femoral circumflex vessels. It arises from the upper part of the external border of the tuberosity of the ischium, and is inserted into the upper part of the linea quadrata—that is, the line which extends vertically downward from the intertrochanteric crest. A bursa is often found between the front of this muscle and the lesser trochanter. Sometimes absent.
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The Obturator externus (Fig. 436) is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis. It arises from the margin of bone immediately around the medial side of the obturator foramen, viz., from the rami of the pubis, and the inferior ramus of the ischium; it also arises from the medial two-thirds of the outer surface of the obturator membrane, and from the tendinous arch which completes the canal for the passage of the obturator vessels and nerves. The fibers springing from the pubic arch extend on to the inner surface of the bone, where they obtain a narrow origin between the margin of the foramen and the attachment of the obturator membrane. The fibers converge and pass backward, lateralward, and upward, and end in a tendon which runs across the back of the neck of the femur and lower part of the capsule of the hipjoint and is inserted into the trochanteric fossa of the femur. The obturator vessels lie between the muscle and the obturator membrane; the anterior branch of the obturator nerve reaches the thigh by passing in front of the muscle, and the posterior branch by piercing it.
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Nerves.—The Glutæus maximus is supplied by the fifth lumbar and first and second sacra nerves through the inferior gluteal nerve; the Glutæi medius and minimus and the Tensor fasciæ latæ by the fourth and fifth lumbar and first sacral nerves through the superior gluteal; the Piriformis is supplied by the first and second sacral nerves; the Gemellus inferior and Quadratus femoris by the last lumbar and first sacral nerves; the Gemellus superior and Obturator internus by the first, second, and third sacral nerves, and the Obturator externus by the third and fourth lumbar nerves through the obturator.
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FIG. 436– The Obturator externus. (See enlarged image)





Actions.—When the Glutæus maximus takes its fixed point from the pelvis, it extends the femur and brings the bent thigh into a line with the body. Taking its fixed point from below, it acts upon the pelvis, supporting it and the trunk upon the head of the femur; this is especially obvious in standing on one leg. Its most powerful action is to cause the body to regain the erect position after stooping, by drawing the pelvis backward, being assisted in this action by the Biceps femoris, Semitendinosus, and Semimembranosus. The Glutæus maximus is a tensor of the fascia lata, and by its connection with the iliotibial band steadies the femur on the articular surfaces of the tibia during standing, when the Extensor muscles are relaxed. The lower part of the muscle also acts as an adductor and external rotator of the limb. The Glutæi medius and minimus abduct the thigh, when the limb is extended, and are principally called into action in supporting the body on one limb, in conjunction with the Tensor fasciæ latæ. Their anterior fibers, by drawing the greater trochanter forward, rotate the thigh inward, in which action they are also assisted by the Tensor fasciæ latæ. The Tensor fasciæ latæ is a tensor of the fascia lata; continuing its action, the oblique direction of its fibers enables it to abduct the thigh and to rotate it inward. In the erect posture, acting from below, it will serve to steady the pelvis upon the head of the femur; and by means of the iliotibial band it steadies the condyles of the femur on the articular surfaces of the tibia, and assists the Glutæus maximus in supporting the knee in the extended position. The remaining muscles are powerful external rotators of the thigh. In the sitting posture, when the thigh is flexed upon the pelvis, their action as rotators ceases, and they become abductors, with the exception of the Obturator externus, which still rotates the femur outward.
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4. The Posterior Femoral Muscles (Hamstring Muscles) (Fig. 434)