- "Quads" redirects here. For other uses see Quad
The quadriceps femoris
for "four-headed [muscle] of the femur"), also called simply the quadriceps
, quadriceps extensor
, or quads
, is a large muscle group that includes the four prevailing muscles on the front of the thigh
. It is the great extensor muscle
of the knee, forming a large fleshy mass which covers the front and sides of the femur
It is 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. o 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).
All four parts of the quadriceps muscle attach to the patella (knee cap) via the quadriceps tendon.
The quadriceps is also involved in Lombard's Paradox.
The proper plural
form of the adjective quadriceps
, a form not in general use; instead, quadriceps
is used in both singular
and plural (i.e., when referring to both legs). The form , though common even in professional contexts, is incorrect. The error may derive from a mistaken belief that quadriceps
is a plural noun (rather than an adjective in the singular), since English typically forms its plurals with the addition of the letter s
to the end of a word stem.
All four quadriceps are powerful extensors of the knee joint. They are crucial in walking, running, jumping and squatting. Because 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.