Which muscles are responsible for flexion of the knee?

The hamstrings and the gastrocnemius are both key muscles involved in the flexion of the knee. The hamstrings group, which includes the biceps femoris, semitendinosus, and semimembranosus, primarily functions to bend the knee. These muscles are located at the back of the thigh and contract to pull the lower leg towards the back of the thigh during knee flexion.

The gastrocnemius, although primarily known for its role in plantar flexion of the ankle, also assists in knee flexion due to its two muscle heads that cross both the knee and ankle joints. When the gastrocnemius contracts, it helps to flex the knee while simultaneously placing some tension on the ankle.

Combining the actions of both the hamstrings and gastrocnemius provides a comprehensive understanding of knee flexion, emphasizing the collaborative nature of these muscles during this movement. This is why the answer encompasses both the hamstrings and the gastrocnemius, reflecting the muscle coordination involved in knee flexion.