Tibial fascia

The fascia of the leg (fascia cruris), which externally envelops the muscles of the leg in the form of a dense sheath, fuses with the periosteum of the anterior edge and the medial surface of the tibia. The anterior and posterior intermuscular septa extend from the fascia of the leg and are attached to the fibula. The anterior intermuscular septum of the leg (septum intermusculare cruris posterius) separates the lateral group of muscles from the anterior and is located between the long and short peroneal muscles at the back and the long extensor of the toes at the front. The posterior intermuscular septum of the leg (septum intermusculare cruris posterius) separates the posterior group of muscles from the peroneal muscles. This septum is located between the peroneal muscles at the front and the soleus muscle at the back. On the back surface of the leg, its fascia is divided into two plates - deep and superficial. The deep plate separates the triceps surae muscle from the long flexors of the toes and the posterior tibialis muscle. The superficial plate covers the triceps muscle from behind, separating it from the subcutaneous tissue. The anterior and posterior groups of the leg muscles are separated not only by the tibia and fibula, but also by the interosseous membrane of the leg stretched between them.

Thus, there are three bone-muscle compartments (beds) on the lower leg, in which three groups of muscles are located: anterior, lateral and posterior. In the anterior muscle compartment, the anterior tibialis muscle lies medially, lateral to it is the long extensor of the fingers, and behind them is the long extensor of the big toe. The anterior tibial artery with the adjacent veins of the same name and the deep peroneal nerve pass through this bone-fascial compartment. The long and short peroneal muscles are located in the lateral compartment. In the upper part of this bone-muscle compartment, there is the superior muscular-peroneal canal (canalis musculoperoneus superior), formed by the two heads of the long peroneus muscle (from the lateral side), as well as the head of the fibula (medially). The common peroneal nerve passes through this canal, which is divided here into the superficial and deep peroneal nerves. The inferior muscular peroneal canal (canalis musculoperoneus inferior) is located behind the middle part of the fibula. Its anterior wall is the aforementioned bone, and its posterior wall is the long flexor of the big toe and the posterior tibialis muscle. The peroneal artery penetrates through this canal from the posterior bone-muscle bed into the lateral one.

The posterior musculoskeletal compartment contains the triceps surae muscle, the long flexor of the big toe and the long flexor of the toes, the posterior tibial and popliteal muscles. This compartment also contains the posterior tibial artery with its veins of the same name and the tibial nerve. This artery and nerve pass from the popliteal fossa into the crural-popliteal canal (Gruber's canal) (canalis cruropopliteus). The anterior wall of the canal is the posterior surface of the posterior tibial muscle. The posterior wall is formed by the soleus muscle with the fascia covering it. The lateral wall of the crural-popliteal canal is the long flexor of the big toe, and the medial wall is the long flexor of the fingers. Through the superior opening of the tibialis popliteal canal, formed by the tendinous arch of the soleus muscle (in front) and the popliteal muscle (behind), the posterior tibial artery (veins are adjacent to it) and the tibial nerve enter the canal. Through the inferior opening, limited by the posterior tibial muscle (in front) and the tendon of the triceps muscle (behind), the vascular-nerve bundle descends onto the posterior surface of the medial malleolus. In the upper part of the interosseous membrane of the leg there is an anterior opening of the tibialis popliteal canal, through which the anterior tibial artery penetrates into the anterior region of the leg. In the upper third of the canal, 4-5 cm below its outlet, the peroneal artery passes, which penetrates into the lateral osteomuscular case through the musculofibular canal.

There are a number of important anatomical structures in the ankle joint area. The medial and lateral malleoli protrude on the sides, and the tendons of the extensors of the foot and toes and the dorsal artery of the foot can be felt on the anterior surface of the joint. Under the skin above the medial and lateral malleoli, there are often subcutaneous malleolus bursae: the subcutaneous bursa of the medial malleolus (bursa subcutanea malleoli medialis) and the subcutaneous bursa of the lateral malleolus (bursa subcutanea malleoli lateralis).

The skin on the body of the foot is thin and mobile. On the anterior surface of the medial malleolus, the beginning of the great saphenous vein of the leg is determined, located in the thickness of the superficial fascia next to the saphenous nerve. Behind the lateral malleolus, there is the beginning of the small saphenous vein of the leg and the sural nerve.

On the medial edge of the foot, 3-4 cm in front of the medial malleolus, the tuberosity of the navicular bone is determined. On the lateral edge of the foot, the tuberosity of the 5th metatarsal bone is palpated. Below the top of the lateral malleolus, there is a protrusion - the lateral process of the talus.

In the lower part of the leg, at the level of the base of the medial and lateral malleoli, the fascia of the leg is significantly thickened by transverse bundles of fibrous fibers. As a result, the upper and lower retainers of the tendons of the extensor muscles of the foot are formed in front, the retainer of the tendons of the flexor muscles is formed behind and medially, and the upper and lower retainers of the tendons of the peroneal muscles are formed behind and laterally. In the posterior region of the ankle joint, the proper fascia of the leg splits, forming a sheath for the tendon (Achilles) of the triceps surae muscle.

The superior retinaculum of the extensor tendons (retinaculum musculorum extensorum superius) connects the fibula and tibia at the level of the medial and lateral malleoli. The inferior retinaculum of the extensor tendons (retinaculum musculorum extensorum inferius) is located below the superior retinaculum, on the anterior surface of the ankle joint. This retinaculum begins on the lateral surface of the calcaneus, below the apex of the lateral malleolus, passes over the extensor tendons where they transition to the dorsum of the foot, and divides into two legs. The superior leg is directed upward and is attached to the anterior surface of the medial malleolus. The inferior leg of the inferior retinaculum approaches the medial edge of the foot and is attached to the navicular and medial cuneiform bones.

From the inner surface of the retainers of the tendons of the extensor muscles to the tibia, to the capsule of the ankle joint, there are septa dividing three fibrous canals. These canals contain the synovial sheaths of the tendons of the extensors of the foot. In the medial canal there is a synovial sheath of the tendon of the anterior tibial muscle (vagina tendinis musculi tibialis anterioris) about 8 cm long. The upper part of this sheath rises above the upper retainer of the tendons of the extensor muscles of the foot 5 cm above the end of the medial malleolus. In the distal direction this sheath continues to the level of the talonavicular joint. In the middle canal there is a synovial sheath of the tendon of the long extensor of the big toe (vagina tendinis musculis extensoris hallucis longi). It is 6-7 cm long and protrudes above the upper edge of the inferior retinaculum of the extensor muscles of the foot. Distally, this synovial sheath reaches the level of the first tarsometatarsal joint. Behind this synovial sheath, the dorsal artery and vein of the foot and the deep peroneal nerve pass in a separate canal. In the lateral fibrous canal lies the synovial sheath of the tendons of the long extensor of the toes (vagina tendinum musculi extensoris digitorum pedis longi) with a length of about 6 cm. Proximally, it rises 2-3 cm above the intermalleolar line (above the upper edge of the inferior retinaculum of the extensor muscles of the foot), and in the distal direction it continues to the level of the cuneiform bones, expanding due to the divergence of the tendons.

Behind the medial malleolus, the fascia of the leg forms a thickening - the retinaculum musculi flexorum, which is thrown from the medial malleolus to the medial surface of the calcaneus. The space under the retinaculum musculi flexorum, called the medial malleolus canal, is limited in front and above by the medial malleolus and talus, and on the lateral side - by the calcaneus. The medial malleolus canal continues anteriorly and downwards into the calcaneal canal - between the calcaneus (laterally) and the muscle that abducts the big toe (medially). Further anteriorly, the calcaneal canal passes into the medial-posterior part of the fascial space of the sole. From the retinaculum of the flexor tendons, fibrous bundles extend deep into the space beneath the retinaculum of the flexor tendons, dividing the space into three fibrous-osseous canals. The first canal (immediately behind the medial malleolus) contains the synovial sheath of the posterior tibialis muscle. The second canal, located posterior to the first and somewhat lateral, contains the sheath of the tendons of the long flexor of the toes. The canal containing the synovial sheath of the tendon of the long flexor of the big toe is located even further posteriorly. Superficially between the canals of the tendons of the long flexors of the toes and the big toe is a fibrous canal in which the posterior tibial artery and veins and the tibial nerve pass.

The length of the synovial sheaths of the tendons of the foot muscles varies. The synovial sheath of the tendon of the posterior tibialis muscle (vagina synovialis tendinis miisculi tibialis posterioris) rises highest (approximately 5 cm above the level of the middle of the medial malleolus), having a length of 7-8 cm. In the distal direction, this synovial sheath continues to the place of attachment of the tendon of this muscle to the tuberosity of the navicular bone. The synovial sheath of the tendon of the long flexor of the toes (vagina synoviaiis tendinis miisculi flexons digitoriim pedis iongi) is 8-9 cm long at the top is located 3-5 cm above the middle of the medial malleolus, and distally reaches the level of the navicular-cuneiform joint. The synovial sheath of the long flexor of the big toe (vagina synoviaiis tendinis musculi flexoris hallucis longi) is about 9 cm long. At the top, it rises 3 cm above the medial malleolus, and on the sole it continues to the lower surface of the first cuneiform bone. The synovial sheath of the tendon of the long flexor of the big toe, adjacent posteriorly closely to the joint capsule of the ankle joint, often communicates with its cavity. Sometimes there is a connection between the synovial sheaths of the tendons of the long flexor of the fingers and the big toe.

Behind the lateral malleolus, the fascia of the leg also thickens, forming the upper and lower retainers of the peroneal tendons: retinaculum musculorum peroneorum (fibularium) superius and retinaculum musculorum peroneomm (fibularium) inferius, which run from the lateral malleolus to the calcaneus. Both retainers of the tendons on the lateral side, and the calcaneus and lateral malleolus medially and in front, limit the lateral malleolar canal, in which the tendons of the long and short peroneus muscles lie. Under the upper retainer of the peroneal tendons, both tendons are located in one common synovial sheath, which protrudes 4-5 cm above the upper retainer of the tendons (2.5-4.5 cm above the middle of the lateral malleolus). The common synovial sheath is divided over a short distance by a thin septum into sheaths for the tendons of the long and short peroneal muscles.

Below the inferior retainer of the peroneal tendon there are already two separate synovial sheaths. Further down, the synovial sheath of the peroneus brevis muscle (its length is about 8 cm) is located immediately behind the lateral malleolus and continues almost to the place of attachment of the tendon of this muscle to the tuberosity of the 5th metatarsal bone. The synovial sheath of the peroneus longus muscle goes to the sole and reaches the line of the calcaneocuboid joint. On the sole there is also a separate synovial sheath of the tendon of the peroneus longus muscle, extending from the groove of the cuboid bone to the place of attachment of its tendon to the medial cuneiform bone and to the bases of the first two metatarsal bones. The total length of the synovial sheath of the tendon of the peroneus longus muscle is about 10.5 cm.

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