Origin: Caudal and medial to the semitendinosus on the lower surface of the rough portion of the tuber ischiadicum.
Insertion: Aponeurosis of origin of the gastrocnemius and the distal end of the medial lip of the femur and medial condyle of the femur.
Action: Extends the hip when the foot is placed on a solid substrate. The cranial head extends the hip and is active during the stance phase of locomotion. The caudal head is a two-joint muscle and can flex the stifle and contribute to hip extension.