Quadriceps femoris muscle

Quadriceps femoris muscle
Muscles of lower extremity. (Rectus femoris removed to reveal the vastus intermedius.)
Latin	musculus quadriceps femoris
Gray's	subject #128 470
Origin	combined rectus femoris and vastus muscles
Insertion	tibial tuberosity
Artery	femoral artery
Nerve	Femoral nerve
Actions	Knee extension; Hip flexion (R.Fem. only)
Dorlands /Elsevier	Quadriceps femoris muscle

"Quads" redirects here. For other uses see Quad

The quadriceps femoris (Latin for "four-headed [muscle] of the femur"), also called simply the quadriceps, quadriceps extensor, 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 the strongest and leanest muscle in the human body.

The quadriceps is also involved in Lombard's Paradox.

The proper plural form of the adjective quadriceps is quadricipes, a form not in general use; instead, quadriceps is used in both singular and plural (i.e., when referring to both legs). The form quadricep [sic], 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.

Portions

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. 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).

All four parts of the quadriceps muscle attach to the patella (knee cap) via the quadriceps tendon.

Actions

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.

Training

In strength training, the quadriceps is trained in isolation with the leg extension exercise, as well as a part of several other lower body exercises.

Additional images

Knee diagram	Capsule of right knee-joint (distended). Lateral aspect.	Cross-section through the middle of the thigh.	Anterior aspect of right leg.
Front and medial aspect of right thigh.	Lateral aspect of right leg.	The leg extension is an isolation exercise.

External links

• Duke Orthopedics quadriceps_muscle
• Muscles/Quadriceps at exrx.net
• Roche Lexicon - illustrated navigator, at Elsevier 39960.000-1
• Anatomy of the Quadriceps Muscles - Fitstep.com

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.