What is the main function of the hamstring muscles?

The main function of the hamstring muscles is indeed the flexion of the knee and extension of the hip. The hamstrings are a group of three muscles located at the back of the thigh, which include the biceps femoris, semitendinosus, and semimembranosus. When these muscles contract, they enable the bending of the knee by pulling the lower leg toward the thigh, which is known as knee flexion. Simultaneously, they also facilitate the extension of the hip joint, allowing for movements such as rising from a seated position or running.

Understanding the specific roles of the hamstring muscles is crucial for activities involving lower limb function, as they play a vital part in stabilizing the knee and hip during various dynamic movements. This complex function is distinct from what the other options describe, making the correct choice clear in reflecting the primary actions associated with this muscle group.