What is the primary function of the hamstring muscles?

The primary function of the hamstring muscles is to flex the knee. The hamstrings are a group of three muscles located at the back of the thigh: the biceps femoris, semitendinosus, and semimembranosus. When these muscles contract, they pull the lower leg backward, which results in the bending of the knee joint.

While the hamstrings also play a role in extending the hip and stabilizing the pelvis during certain movements, their main and most recognized function is to facilitate knee flexion. This action is essential for activities such as walking, running, and jumping, where the knee must be bent to allow for proper movement and balance. Adduction of the thigh is primarily performed by other muscle groups, such as the adductors, and is not a primary function associated with the hamstrings. Thus, the identification of knee flexion as the primary role emphasizes the importance of these muscles in lower extremity movements.