The semimembranosus is one of the three muscles that make up the hamstring group located at the back of the thigh. It plays a crucial role in bending the knee and extending the hip. This muscle originates from the ischial tuberosity of the pelvis and inserts into the medial condyle of the tibia, contributing to the stability of the knee joint. In addition to its primary functions, the semimembranosus assists in rotating the thigh inward when the knee is bent. It works in conjunction with the other hamstring muscles, including the semitendinosus and biceps femoris, to facilitate various movements during activities like walking, running, and jumping.