plantaris

noun

plan·​tar·​is plan-ˈtar-əs 

plural plantares -ˌēz 

: 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 flexes the leg at the knee and the foot at the ankle see plantar interosseus, verruca plantaris