Gastrocnemius

The gastrocnemius (Latin: musculus gastrocnemius) is a large muscle located in the posterior compartment of the leg. It is the most superficial muscle of the posterior leg and, together with the soleus, forms a muscle complex known as the triceps surae. The gastrocnemius is a fundamental muscle for walking and posture as it affects the entire lower limb. Besides the gastrocnemius, the superficial layer of the posterior leg also includes the plantaris.

Origin

The gastrocnemius contains two heads, and each of them has a different site of origin. The medial head of the muscle arises from the medial condyle of the femur, while the lateral head originates from the lateral condyle of the femur.

Insertion

The gastrocnemius inserts on the posterior surface of the calcaneus via Achilles tendon. Both heads of the muscle join together and later merge with the soleus tendon approximately in the middle third of the leg to form a common tendon called Achilles or calcaneal tendon.

Action

The gastrocnemius provides foot plantar flexion at the talocrural (ankle) joint. Also, it is responsible for the flexion of the leg at the knee joint.

Innervation

The gastrocnemius is innervated by the tibial nerve (S1 - S2) - a terminal branch of the sciatic nerve.

Blood supply

The gastrocnemius receives arterial blood supply from the sural arteries - branches of the popliteal artery.