Posterior region of leg

The posterior region of leg typically corresponds to the posterior leg compartment.

Fascia and skin:

• The muscles, ligaments, and neurovasculature of the posterior region of leg are enveloped by layers of skin and superficial and deep fascia.

• The deep fascia thickens around the ankle joint, forming a flexor retinaculum that wraps around the long tendons of the posterior leg muscles to prevent bowstringing during ankle movements. There are two other retinacula in the ankle region: the peroneal retinaculum (for the lateral compartment of the leg) and the extensor retinaculum (for the anterior region of the leg).

Musculature:

The muscles of the posterior region of leg are divided into superficial and deep groups:

• The superficial group consist of the gastrocnemius, soleus, and plantaris muscles. They attach to the calcaneum or the heel bone via a common Achilles tendon and contribute to knee and ankle joint flexion (plantar flexion). The gastrocnemius and soleus are the largest calf muscles, with the soleus being stronger but the gastrocnemius having faster action. As a result, the gastrocnemius muscle generates the primary propulsive force during walking and running, while the soleus functions as the primary postural muscle.

  Please note that the calf muscles also play a crucial role in circulation. Contraction of these muscles, particularly the soleus, aids in venous return from the lower limb.

• The deep group comprises the tibialis posterior, flexor hallucis longus and flexor digitorum longus muscles. They pass through the tarsal tunnel beneath the flexor retinaculum and insert into the sole, enabling plantar flexion at the ankle joint. The tibial nerve and posterior tibial vessels also traverse the tarsal tunnel, entering the sole as the medial and lateral plantar nerves and vessels.

• The popliteus muscle is located deeply within. It originates from the lateral femoral condyle and inserts into the upper posterior aspect of the tibia, above the soleal line. It pulls the lateral condyle of the femur, causing external rotation of the femur on a fixed tibia to unlock the knee joint at the beginning of flexion.

Neurovasculature:

• The sciatic nerve typically bifurcates in the upper portion of the popliteal fossa into the common fibular (common peroneal) and tibial nerve branches. The tibial nerve innervates all the flexor muscles, both superficial and deep groups.

• The blood supply to the posterior region of leg is provided by the posterior tibial vessels.