Gastrocnemius is the most superficial of the muscles of the posterior compartment of the lower limb distal to the knee.
It arises from two heads that converge to form the inferior border of the popliteal fossa. The lateral head arises from the posterolateral surface of the lateral condyle of the femur. The medial head arises from the popliteal surface of the femur superior to the medial condyle.
With soleus, it converges on the tendo calcaneus to insert into the middle of the posterior surface of the calcaneus. Just superior to this insertion, a small bursa separates the tendon from the bone.
Gastrocnemius is innervated by the tibial nerve (S1,S2).
It acts to:
- plantarflex the foot at the ankle
- raise the heel during walking
- weakly flexes the knee