Bone: Patella tendonismness
Right knee
Gray's	subject #60 255
MeSH	Patella

The patella, also known as the knee cap or kneepan, is a thick, circular-triangular bone which articulates with the femur and covers and protects the knee joint. It is the largest sesamoid bone in the human body. It is attached to the tendon of the quadriceps femoris muscle, which contracts to extend/straighten the knee. The vastus intermedialis muscle is attached to the base of patella. The vastus lateralis and vastus medialis are attached to lateral and medial borders of patella respectively.

The patella is stabilized by the insertion of vastus medialis and the prominence of the anterior femoral condyles, which prevent lateral dislocation during flexion. The retinacular fibres of the patella also stabilize it during exercise.

The primary functional role of the patella is knee extension. The patella increases the leverage that the tendon can exert on the femur by increasing the angle at which it acts.

The patella ossifies between the ages 2-6 years. In some people it may be absent congenitally or hypoplastic. In 2% of the population there is a bipartite patella, which is usually asymptomatic. Direct trauma, however, may produce symptoms that mimic those of a fracture.

The patella has convergently evolved in placental mammals and birds; marsupials have only rudimentary, non-ossified patellae.^[1] In more primitive tetrapods, including living amphibians and reptiles, the muscle tendons from the upper leg are attached directly to the tibia, and the patella is not present.^[2]

[edit] See also

• Patellar reflex
• Patellar dislocation
• Lateral retinaculum
• Lateral release

[edit] Additional images

Lower extremity	Left patella - anterior aspect	Left patella - posterior aspect	Right knee-joint. Anterior view.
Sagittal section of right knee-joint.	Capsule of right knee-joint (distended). Lateral aspect.	Front and medial aspect of right thigh.	Lateral aspect of right leg.

[edit] References

1. ^ Herzmark MH (1938). "The Evolution of the Knee Joint". J Bone Joint Surg Am 20: 77–84. http://www.ejbjs.org/cgi/reprint/20/1/77.pdf. Retrieved 2007-11-17. 
2. ^ Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. p. 205. ISBN 0-03-910284-X. 

[edit] External links

Wikimedia Commons has media related to: Patella

• The KNEEguru - educational site packed with knee content with sections on the patella
• SUNY Figs 12:01-15

v • d • e Bones of lower limbs (TA A02.5.04-18, GA 2.242-277) Femur upper extremity head (fovea) · neck · greater trochanter (trochanteric fossa) · lesser trochanter · intertrochanteric line · intertrochanteric crest · quadrate tubercle body linea aspera · gluteal tuberosity / third trochanter · pectineal line lower extremity adductor tubercle · patellar surface · epicondyles (lateral, medial) · condyles (lateral, medial) · intercondylar fossa Crus Tibia upper extremity Gerdy's tubercle · condyles (lateral, medial) · intercondylar eminence (lateral/medial intercondylar tubercle) · posterior/anterior intercondylar area body tuberosity · soleal line lower extremity medial malleolus · fibular notch Fibula head · body · lateral malleolus Other patella (apex of patella) Foot Tarsus calcaneus (sustentaculum tali, trochlear process) · talus (body, neck, head) · navicular · cuboid · cuneiform (medial, intermediate, lateral) Metatarsus 1st metatarsal · 2nd · 3rd · 4th · 5th Other phalanges of the foot

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