The “Quads” (Quadriceps femoris)
The quadriceps femoris – Latin for “four-headed muscle of the femur” – also called simply the quadriceps, quadriceps extensor or just the “quads”, is a large muscle group that includes the four prevailing muscles on the front of the thigh.
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, plays the important role of stabilizing the patella and the knee joint during gait.
The quadriceps is the great extensor muscle of the knee, forming a large fleshy mass which covers the front and sides of the femur. It is the strongest and leanest muscle in the human body.
The Quads are subdivided into four separate portions or ‘heads’, which have received distinctive names:
- Rectus femoris occupies the middle of the thigh, covering most of the other three quadriceps muscles. It originates on the ilium. It is named from its straight course.
The other three lie deep to rectus femoris and originate from the body of the femur, which they cover from the trochanters to the condyles :
- Vastus lateralis is on the lateral side of the femur (i.e. on the outer side of the thigh).
- Vastus medialis is on the medial side of the femur (i.e. on the inner part thigh).
- Vastus intermedius lies between vastus lateralis and vastus medialis on the front of the femur (i.e. on the top or front of the thigh), but deep to the rectus femoris. Typically, it cannot be seen without dissection of the rectus femoris.