The quadriceps femoris consists of four individual muscles; three vastus muscles and the rectus femoris. They form the main bulk of the thigh, and collectively are one of the most powerful muscles in the body. The quadriceps femoris unite proximal to the knee and attach to the patella via the quadriceps tendon. In turn, the patella is attached to the tibia by the patella ligament.
All four quadriceps are powerful extensors of the knee joint. They are crucial in walking, running, jumping and squatting. Because the rectus femoris attaches to the ilium, it is also a flexor of the hip. 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.