It is the sole extensor muscle of the knee, forming a large fleshy mass which covers the front and sides of the femur.

The quadriceps femoris muscle is subdivided into four separate muscles (the 'heads'),[1][2] with the first superficial to the other three over the femur (from the trochanters to the condyles): The rectus femoris arises from the anterior inferior iliac spine and from the superior edge of the acetabulum.

In addition, cadaver studies have confirmed the presence of a sixth muscle, the tensor vastus intermedius.

[1][4] This action is also crucial to walking or running, as it swings the leg forward into the ensuing step.

The quadriceps, specifically the vastus medialis, play the important role of stabilizing the patella and the knee joint during gait.