What action is performed by the quadriceps at the knee joint?

The quadriceps muscle group is primarily responsible for extending the knee joint. This action occurs when the quadriceps contract, pulling on the patellar tendon, which ultimately straightens the leg. The quadriceps consist of four muscles: the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius, all of which contribute to this extension movement.

This extension is essential for several everyday activities, such as walking, running, squatting, and jumping, where straightening the knee is necessary for proper function. Understanding the role of the quadriceps in knee extension is crucial for Pilates instructors, as many movements aim to strengthen and stabilize this muscle group to promote effective lower body function and injury prevention.