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Gastrocnemius

The gastrocnemius  (also gastrocnemius muscle, latin: musculus gastrocnemius) is a superficial muscle of the posterior group of the lower leg muscles.

Origin

The gastrocnemius originates with two heads: the medial and the lateral head. The medial head of the gastrocnemius arises from the medial condyle, while the lateral head originates from the lateral condyle of the femur.

Insertion

The gastrocnemius inserts onto the calcaneal tuberosity of the calcaneus, as its both heads join with the tendon of the soleus in the midline of the lower leg in a tendon (Achilles tendon).

Action

The main function of the gastrocnemius is flexion of the knee. Contraction of the medial head of the gastrocnemius rotates the leg medially (internal rotation of the leg), while the activation of the lateral head rotates the leg laterally (external rotation of the leg).

Innervation

The gastrocnemius is innervated by the tibial nerve, a terminal branch of the sciatic nerve.