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.

Contents 1 Portions 2 Actions 3 Training 4 Additional images 5 External links

[edit] 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.

[edit] 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.

[edit] 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. It is very important in all sports to have strong quadriceps muscles; if not they are commonly torn.

[edit] 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.

[edit] 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.

v • d • e List of muscles of lower limbs (TA A04.7, GA 4.465) ILIAC Region / ILIOPSOAS psoas major/psoas minor · iliacus BUTTOCKS gluteals: (maximus, medius, minimus) · tensor fasciae latae lateral rotator group: quadratus femoris · inferior gemellus · obturator internus · superior gemellus · piriformis THIGH / compartments Anterior sartorius · quadriceps (rectus femoris, vastus lateralis, vastus intermedius, vastus medialis) · articularis genu Posterior/hamstring biceps femoris · semitendinosus · semimembranosus Medial pectineus · obturator externus · gracilis · adductor (longus, brevis, magnus) Fascia Femoral sheath (Femoral canal) · Femoral ring Adductor canal · Adductor hiatus fascia lata (Iliotibial tract, Lateral intermuscular septum of thigh, Medial intermuscular septum of thigh, Fascia cribrosa/Saphenous opening) LEG/ Crus/ compartments Anterior tibialis anterior · extensor hallucis longus · extensor digitorum longus · peroneus tertius Posterior superficial · triceps surae (gastrocnemius, soleus, Achilles tendon) · plantaris deep · tarsal tunnel (flexor hallucis longus, flexor digitorum longus, tibialis posterior) · popliteus Lateral peroneus muscles (longus, brevis) Fascia Pes anserinus crural fascia (Anterior crural intermuscular septum, Posterior crural intermuscular septum, Transverse intermuscular septum) FOOT Dorsal extensor hallucis brevis · extensor digitorum brevis Plantar 1st layer (abductor hallucis, flexor digitorum brevis, abductor digiti minimi) · 2nd layer (quadratus plantae, lumbrical muscle) · 3rd layer (flexor hallucis brevis, adductor hallucis, flexor digiti minimi brevis) · 4th layer (dorsal interossei, plantar interossei) Fascia Plantar fascia retinacula (Peroneal, Inferior extensor, Superior extensor, Flexor)