The largest compartment of the leg is the posterior, which is divided into two layers and comprises seven muscles. The layers are superficial and deep, separated by fascia.
- This group of muscles naturally antagonizes the anterior compartment.
- The main functions of the muscles of this area are plantarflexion and inversion of the foot.
- Due to the constant resistance against gravity during standing and when performing locomotion movements, the muscles that integrate this compartment of the leg are more strongly developed than the other groups.
Superficial layer
The muscles of this layer attach to the calcaneus bone shaping the typical “calf” of the ankle. Their insertion follows the calcaneal tendon. By working together, these muscles move the body forward from the planted foot during the walk. When standing, elevate the body onto the toes.
The muscles that comprise the superficial layer of the posterior compartment are:
- The gastrocnemius
- The plantaris
- The soleus
The three muscles receive innervation from the S1 and S2 branches of the tibial nerve.
Gastrocnemius
The gastrocnemius muscle is the largest muscle of the leg, and locates superficially at the posterior compartment. It has two heads for its insertion: medial and lateral.
- Medial head: originates from the distal femur, posterior to the adductor tubercle, and superior to the articular side of the medial condyle of the femur.
- Lateral head: elongates from the superolateral surface of the femoral condyle.
- Both