Which of the following muscles aids in flexing the knee and extending the hip?

• A. Gracilis
• B. Biceps femoris
• C. Adductor longus
• D. Semitendinosis

Answer: (B)

The biceps femoris is one of the muscles that comprises the hamstring group, which is primarily responsible for actions involving both the flexion of the knee and extension of the hip. When the knee is flexed, the biceps femoris works by contracting to bring the lower leg towards the thigh. Simultaneously, when the hip is extended, the muscle plays a crucial role as a powerful extensor at the hip joint.

In the context of the knee flexion, the biceps femoris allows for substantial movement, aiding activities such as walking, running, and jumping, where bending the knee is essential. Additionally, when the hip joint is extended, this muscle helps stabilize the pelvis and facilitate movements that require force generation from the lower limb.

Other muscles listed may have roles in the hip or knee movements but cannot perform both functions simultaneously in the same capacity as the biceps femoris.