leg muscle plantaris muscle 2019-09-29T14:19:49Z A small muscle of the calf of the leg that arises from the lower end of the femur and the posterior ligament of the knee joint, is inserted with the Achilles tendon by a very long slender tendon into the calcaneus, and weakly felxes the leg at the knee and the foot at the ankle. BTO:0006312 BrendaTissueOBO Marion musculus plantaris plantar muscle plantaris