Which muscle group is primarily responsible for knee extension?

The quadriceps muscle group is primarily responsible for knee extension. This group consists of four muscles located at the front of the thigh: the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. During activities such as standing up from a seated position, kicking a ball, or performing squats, the quadriceps contract to extend the leg at the knee joint. This action is essential for many functional movements, athletic activities, and daily tasks.

In contrast, the hamstrings, located at the back of the thigh, are primarily involved in knee flexion rather than extension. The gastrocnemius, although it crosses the knee joint and is active during movements involving ankle flexion, also contributes to knee flexion rather than extension. The sartorius muscle assists in movements such as hip flexion, but it does not play a primary role in extending the knee. Thus, the quadriceps are unequivocally the key muscles involved in knee extension.