Muscles of lower leg

Muscles of the shin, like other muscles of the lower limb, are well developed, which is determined by the function they perform in connection with the upright walking, static and dynamics of the human body. Having a vast beginning on the bones, intermuscular septa and fasciae, the muscles of the shins act on the knee, ankle joints and joints of the foot.

There are anterior, posterior and lateral groups of leg muscles. The front group includes the anterior bolepteric muscle, the long extensor of the fingers, the long extensor of the thumb. To the posterior group belong the triceps muscle of the shank (consisting of gastrocnemius and soleus muscles), plantar and popliteal muscles, a long flexor of the fingers, a long flexor of the big toe, a posterior lumbar muscle. The lateral group of the tibia includes the short and long fibular muscles.

Anterior group of calf muscles

The anterior tibialis muscle (m.tibialis anterior) is located on the front side of the shin. It begins on the lateral condyle and the upper half of the lateral surface of the tibia, as well as the adjacent part of the interosseous membrane and on the fascia of the tibia. At the distal third of the tibia, the muscle bundles pass into a long tendon that passes under the upper and lower extensor tendons, anterior to the ankle joint. Further, the tendon circumscribes the medial edge of the foot and attaches to the plantar surface of the medial sphenoid bone and the base of the metatarsal bone.

Function: unbends the foot in the ankle joint, simultaneously lifts the medial edge of the foot and turns it outward (supination), strengthens the longitudinal arch of the foot. With a fixed foot, the shin is tilted forward; helps maintain the shin in an upright position.

Innervation: deep peroneal nerve (LIV-SI).

Blood supply: anterior tibial artery

The long extensor of the fingers (m.extensor digitorum longus) - the muscle is pinnate, begins on the lateral condyle of the tibia, the anterior surface of the fibula, the upper third of the interosseous membrane, the fascia and the anterior intermuscular septum of the lower leg. Going to the rear of the foot, the muscle passes behind the upper and lower supports of the extensor tendons. At the level of the ankle, the muscle is divided into 4 tendons, which are enclosed in the common for them synovial vagina. Each tendon is attached to the back of the base of the middle and distal phalanges of the II-V fingers.

From the lower part of the muscle is separated a small bundle, called the third fibular muscle (m.peroneus tertius), the tendon of which is attached to the base of the metatarsal bone.

Function: unbends the II-V fingers in the metatarsophalangeal joints, as well as the foot in the ankle joint. The third fibular muscle lifts the lateral edge of the foot. With the strengthened foot, the long extensor of the fingers keeps the shin in an upright position.

Innervation: deep peroneal nerve (LIV-SI). Blood supply: anterior tibial artery.

The long extensor of the big toe (m.extensor hallucis longus) is located between the anterior tibial muscle medially and the long extensor of the fingers laterally; partially covered by the front. It begins on the middle third of the anterior surface of the fibula, the interosseous membrane of the shin. The tendon of the muscle passes down to the rear of the foot under the upper and lower retainers of the extensor tendons in a separate synovial vagina and is attached to the distal phalanx of the big toe. Individual bundles of the tendon can also be attached to the proximal phalanx.

Function: unbends the thumb of the foot; participates also in the extension of the foot in the ankle joint.

Innervation: deep peroneal nerve (LIV-SI).

Blood supply: anterior tibial artery.

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Posterior group of calf muscles

Muscles of the posterior group form two layers - surface and deep. The superficially lying triceps muscle of the tibia is more strongly developed, which creates the characteristic roundness of the lower leg for the person. The deep layer is formed by a small popliteal muscle and 3 long muscles: the long flexor of the fingers (located most medially), the posterior tibialis muscle (occupies an intermediate position) and the long flexor of the large toe (located laterally).

Surface layer of posterior group of lower leg muscles

The triceps groin (m.triceps surae) consists of two muscles - the gastrocnemius muscle, which is superficially located, and the soleus muscle hidden under the calf muscle. The gastrocnemius muscle belongs to the two-joint muscles, it acts on two joints - the knee and ankle, while the soleus muscle is single-joint - it acts only on the ankle joint.

The gastrocnemius muscle (m.gastrocnemius) has two heads: medial and lateral, the surface layers of which are represented by strong tendon bundles. The lateral head (caput laterale) begins on the external surface of the lower epiphysis of the femur above the lateral condyle. The medial head (caput mediate) begins on the medial condyle of the thigh. Under each head of the gastrocnemius muscle is a synovial bag. Between the lateral head and the capsule of the knee joint is the lateral subculture bag of the gastrocnemius muscle (bursa subtendinea musculi gastrocnemii lateralis). Between the medial head and the capsule of the joint is the medial clinging bag of the gastrocnemius muscle (bursa subtendinea musculi gastrocnemii medialis). Both bags, as a rule, communicate with the cavity of the knee joint.

In the middle of the shin, the two gastrocnemius muscles turn into a thick tendon that narrows downward and merges with the tendon of the soleus muscle, forming a calcaneal tendon (tendo calcaneus, s. Achilli), which attaches to the calcaneal tubercle. Between the tendon and the calcaneus there is a heel (Achilles) tendon bag (bursa tendinis calcanei, s. Achillis).

The soleus muscle (m.soleus) is thick, flat, lying under the calf muscle. Front of her are the muscles of the deep layer. The soleus muscle has a vast origin on the posterior surface of the ribs (on the soleus muscle line) and on the tendon arc (arcus tendineus musculi solei), which swings between the tibial and fibular bones. The soleus muscle has a pinnate structure, passes into a flat tendon that participates in the formation of the calcaneal tendon.

Function: the triceps muscle flexes the lower leg and the foot (plantar flexion); with a fixed foot, restrains the shin on the talus bone, not allowing it to tip over.

Innervation: the tibial nerve (LIV-SI).

Blood supply: posterior tibial artery.

Plantar muscle

(m.plantaris) is unstable, has a small abdomen and a long thin tendon. It begins on the lateral epicondyle of the femur and on the oblique popliteal ligament. The tendon of this muscle passes between the gastrocnemius and soleus muscles, is attached to the medial edge of the calcaneal tendon, together with which it is attached to the calcaneal tubercle.

Function: tightens the capsule of the knee joint, participates in the bending of the lower leg and the foot.

Innervation: tibial nerve (LIV-SII).

Blood supply: popliteal artery.

Deep layer of posterior group of calf muscles

The deep layer is formed by 4 muscles: the popliteal, long flexor of the fingers, the long flexor of the big toe and the posterior tibial muscle, which are separated from the soleus muscle by the deep fascia fascia plate.

The popliteal muscle (m.popliteus) lies deep in the popliteal fossa. It begins with a thick tendon on the outer surface of the lateral condyle of the thigh (below the attachment of the fibular collateral ligament). The muscle is attached to the posterior surface of the capsule of the joint and lies below the arcuate popliteal ligament, on which its medial fascicles begin. The muscle is attached to the triangular area on the posterior surface of the tibia, above the soleus muscle line.

Function: bends the shin, turning it to the inside; tightens the capsule of the knee joint, protecting the synovial membrane from infringement.

Innervation: tibial nerve (LIV-SII).

Blood supply: popliteal artery.

The long flexor of the fingers (m.flexor digitorum longus) has a two-pinnate structure, begins with fleshy bundles on the posterior surface of the tibia below the soleus muscle line, as well as on the fascia and posterior intermuscular septum of the tibia. It is located behind and medial to the posterior tibial muscle. The tendon of the long flexor of the fingers goes down, crosses behind and from the lateral side the tendon of the posterior tibial muscle. Then the tendon of the muscle passes to the sole of the foot behind the medial malleolus under the flexor tendon retainer in a separate synovial vagina (between the tendons of the posterior tibial muscle medially and the long flexor of the thumb laterally). Then the tendon curves around the back and below the support of the talus bone. Located above the short flexor of the fingers, it is divided into 4 separate tendons, which attach to the distal phalanges of the II-V fingers, pre-sampling the tendons of the short flexor of the fingers (similar to the tendons of the deep flexor of the fingers on the wrist).

Function: bends the distal phalanges of II-V fingers; bends the foot, turning it outward.

Innervation: tibial nerve (LIV-SII).

Blood supply: posterior tibial artery.

Long flexor of the big toe

(m.flexor hallucus longus) - a bicefish muscle, begins on the lower two thirds of the fibula, the interosseous membrane, the posterior intermuscular septum of the shin. It is located laterally and behind the posterior tibial muscle. The tendon of the long flexor of the big toe passes under the flexor tendon holder behind the medial malleolus and lateral to the tendon of the long flexor of the fingers in a separate synovial vagina. Further, the tendon of the long flexor of the large toe of the foot lies in the same groove on the posterior process of the talus, passing forward under the support of the talus bone. Having reached the plantar surface of the big toe, the tendon of the long flexor of the thumb is attached to its distal phalanx. On its way to the foot, this tendon crosses with the tendon of the long flexor of the fingers (lies under it). Throughout the sole surface of the I metatarsal bone, the tendon of the long flexor of the large toe of the foot lies between the medial and lateral abdomen of the short flexor of the large toe.

Function: bends the thumb of the foot, participates in bending (supination) and bringing the foot; strengthens the longitudinal arch of the foot.

Innervation: tibial nerve (LIV-SII).

Blood supply: posterior tibial and peroneal arteries.

The posterior tibialis muscle (m.tibialis posterior) is located deep on the posterior surface of the tibia between the long flexor of the fingers (medially) and the long flexor of the big toe (laterally). It begins on the back of the fibula (between the medial crest and the intercostal margin), the lower surface of the lateral condyle and on the upper two thirds of the tibia (below the soleus muscle line) and the interosseous epibody of the shin.

The muscle continues into a strong tendon that lies in the groove on the back of the medial malleolus in front of the tendon of the long flexor of the fingers (under the flexor tendon holder). On the sole surface of the foot, the tendon is attached to the tuberosity of the scaphoid bone, to all 3 wedge-shaped bones, and also to the base IV (sometimes V) of the metatarsal bone.

Function: bends the foot (plantar flexion), leads to the foot and supplements it.

Innervation: tibial nerve (LIV-SII).

Blood supply: posterior tibial artery.

Lateral group of leg muscles

The lateral group is represented by a long and short fibular muscle that is located on the lateral surface of the tibia under the fascia between the anterior and posterior intermuscular septa.

The long peroneal muscle (m.peroneus longus) is bifid, superficial, begins on the head and upper two thirds of the lateral surface of the fibula, on the lateral condyle of the tibia, on the fascia of the shank and on the intermuscular septum. At the level of the ankle, the tendon of the muscle, passing the lateral ankle from behind, passes first under the upper retina of the tendons of the peroneus muscles in the common synovial vagina with the tendon of the short fibular muscle and then in the groove on the heel bone (under the lower support of the tendons of the peroneus muscles). On the sole, the tendon of the long fibular muscle passes obliquely forward and medially, lies in the same groove of the cuboid bone in a separate (own) synovial vagina. The tendon is attached to the base of I and II metatarsal bones and to the medial sphenoid bone.

In those points where the tendon changes its direction (behind the lateral ankle and the cuboid bone), it usually thickens due to the fibrous cartilage or sesamoid bone formed in its thickness.

Function: bends the foot, raises its lateral edge (pronation), strengthens the transverse and longitudinal arches of the foot.

Innervation: superficial peroneal nerve (LIV-SI).

Blood supply: lateral lower knee artery, peroneal artery.

The short peroneal muscle (m.peroneus brevis) is bifid, begins on the lower two-thirds of the lateral surface of the fibula and on the intermuscular septum. The tendon of the muscle passes to the foot behind the lateral ankle under the fibular tendon retainer, lying in the common synovial vagina together with the tendon of the long fibular muscle. At the lower edge of this retainer the tendon of the short fibular muscle turns forward and passes along the outside of the heel bone under the peroneal block to the attachment site on the base of the metatarsal bone.

Function: lifts the lateral edge of the foot; prevents the foot from turning to the inside; bends the foot (plantar flexion).

Innervation: superficial peroneal nerve (LIV-SI).

Blood supply: peroneal artery.