Which muscles contribute to knee flexion?

Knee flexion primarily involves muscles that are responsible for bending the knee joint. The hamstrings are key players in this action as they consist of three muscles (biceps femoris, semitendinosus, and semimembranosus) that work together to flex the knee. In addition, the gastrocnemius, which is part of the calf muscles, also crosses the knee joint and assists in knee flexion when the ankle is in a plantarflexed position.

The correct answer highlights the hamstrings, gluteus maximus, and gastrocnemius as contributors to knee flexion, which is accurate because these muscles actively pull the leg towards the back of the thigh when they contract. The gluteus maximus, while primarily known for hip extension, can assist in knee flexion through its influence on hip positioning, especially when considering functional movements like squats or lunges.

Conversely, the other options listed do not accurately represent the muscles responsible for knee flexion. The patellar tendon and quadriceps muscles (like vastus medialis and vastus lateralis) are more involved in knee extension rather than flexion. Thus, the focus on the hamstrings and gastrocnemius in the correct answer provides