gastrocnemius

The gastrocnemius is a major superficial muscle of the posterior leg and one of the two heads of the triceps surae, the other being the soleus. Together with the plantaris, it contributes to plantar flexion of the foot and knee flexion, enabling movements such as standing on tiptoe and push-off during gait.

The muscle has two heads: the medial head originates from the medial femoral condyle, and the lateral head from the lateral femoral condyle. The heads fuse into the strong Achilles tendon, which inserts on the posterior calcaneus. The gastrocnemius crosses both the knee and ankle joints.

Innervation is via the tibial nerve, a branch of the sciatic nerve. Blood supply comes from branches of the popliteal artery. Functionally, it plantarflexes the foot and assists knee flexion; it is particularly active during rapid or forceful movements such as sprinting or jumping, whereas the soleus dominates quiet standing.

Clinical significance includes gastrocnemius strains and ruptures, commonly referred to as tennis leg. Symptoms include sudden calf pain and swelling with reduced plantarflexion. Diagnosis uses physical examination and imaging. Treatment ranges from rest and rehabilitation to surgical repair in complete ruptures; rehabilitation emphasizes gradual loading and flexibility.