Muscle · Lower leg

Plantaris

Musculus plantaris

A small spindle of muscle high in the back of the knee with a very long, very thin tendon — a belly of a few centimetres feeding a cord that runs the whole length of the calf. It starts just above the outer head of gastrocnemius on the femur, slips down between gastrocnemius and soleus, and ends on the heel bone alongside or blended with the Achilles tendon. Its pull is trivial: it bends the knee and points the foot in company with muscles many times its size, and it is absent altogether in a proportion of legs without anyone noticing. It is met mostly as the thin white cord that surprises people who expect the calf to contain two muscles.