The larger, outer muscle of the calf that gives the lower leg its shape is the gastrocnemius.
The gastrocnemius is the prominent, superficial calf muscle visible beneath the skin. It has two heads, one arising from each femoral condyle near the knee, giving the upper calf its characteristic rounded shape. Because it crosses both the knee and ankle, it helps flex the knee and point the foot downward, a movement called plantar flexion.
The soleus lies deeper beneath the gastrocnemius and also contributes to the calf’s strength and shape. Together, the gastrocnemius and soleus are commonly grouped as the triceps surae. Their shared force is transmitted through the calcaneal tendon, better known as the Achilles tendon, which attaches to the heel bone.
A common mix-up is identifying the Achilles tendon as the calf muscle itself. The tendon is tough connective tissue, not muscle. The tibialis anterior is located on the front of the lower leg, where it lifts the foot upward. The name gastrocnemius comes from Greek roots meaning roughly “belly of the leg,” referring to its bulging appearance.