Both the semimembranosus and semitendinosus extend the thigh and assist in hip joint medial rotation. Because their tendon of insertion is on the medial side of the knee joint, they are also known as the medial hamstrings.
The semitendinosus attaches to the tuberosity of the ischium at the upper end.
The semitendinosus attaches to the posterior medial condyle of the tibia at the lower end.
Knee joint flexion. The semitendinosus also extends the thigh and assists in hip joint medial rotation.