The semimembranosus muscle is located in the posterior compartment of the thigh. It is one of the hamstring muscles and is situated medially, contributing to the musculature at the back of the thigh. It is a relatively flat and broad muscle.
Originating from the ischial tuberosity, the semimembranosus takes its starting point from the bony prominence on the posterior aspect of the hip bone.
The muscle inserts into the posterior aspect of the medial condyle of the tibia. Additionally, it has an attachment to the posterior part of the lateral condyle of the femur through the oblique popliteal ligament. This insertion site establishes a connection with the proximal part of the tibia and the femur.
Functionally, the semimembranosus is a powerful flexor of the knee joint and plays a role in medial rotation of the tibia. It is actively engaged in movements like bending the knee, such as during walking or running, and contributes to the stability of the knee joint. Additionally, the muscle is involved in hip extension, aiding in movements where the thigh moves backward. The semimembranosus is integral to the coordinated actions of the hamstring muscles and their role in lower limb biomechanics.