It passes posterior to the knee joint in an inferomedial direction and becomes tendinous distally to insert into the Achilles tendon.

Decussation of the lateral corticospinal tract occurs in the medullary pyramids, then the fibers continue down the contralateral side of the spinal cord.

The plantaris muscle may also provide proprioceptive feedback information to the central nervous system regarding the position of the foot.

Although pain in the calf can be attributed to a rupture of the plantaris muscle, recent ultrasound research has shown that tennis leg more commonly arises from tears in the musculotendinous junction of the medial gastrocnemius.

[6] Injury may occur from running, jumping, or pushing off one leg in sports such as tennis, basketball and soccer, which require quick foot movement in a certain direction.

[7] Symptoms of a plantaris muscle rupture may include an audible popping sound in the area during physical activity, swelling, pain in the back of the lower leg, and persistent soreness.