Plantaris is long, thin muscle extending behind the knee and into the sural region (calf) of the posterior leg. It forms, together with gastrocnemius and soleus, the superficial group of the posterior compartment of the leg. The muscle belly is variable both in thickness and length. Sometimes the muscle has two bellies separated by a tendon, and in around 10% of the population, plantaris is absent altogether. There is also an ongoing debate about its function. Plantaris gets its name because in