Patella
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2008-06-20T12:27:11Z
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{{otheruses}}
{{Infobox Bone |
Name = Patella |
Latin = |
GraySubject = 60 |
GrayPage = 255 |
Image = Knee diagram.svg |
Caption = Knee diagram |
Image2 = |
Caption2 = |
Origins = |
Insertions = |
Articulations = |
MeshName = Patella |
MeshNumber = A02.835.232.043.650.624 |}}
The '''patella''' or '''kneecap''' is a thick, 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|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 stabilised 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 stabilise it during exercise.
The primary functional role of the patella is knee extension. The patella increases the [[lever]]age that the tendon can exert on the femur by increasing the angle at which it acts.
The patella [[Ossification|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.
Regarding non-human animals, the patella is fully developed only in [[Eutheria|placental mammals]]; marsupials have only rudimentary, non-ossified patellae.<ref>{{cite journal|author=Herzmark MH|title=The Evolution of the Knee Joint| url=http://www.ejbjs.org/cgi/reprint/20/1/77.pdf| accessdate=2007-11-17| journal=J Bone Joint Surg Am| year=1938| volume=20| pages=77–84}}</ref>
==See also==
* [[Patellar reflex]]
* [[Lateral retinaculum]]
==Additional images==
<gallery>
Image:Illu lower extremity.jpg|Lower extremity
Image:Patella_ant.jpg|Left patella - anterior aspect
Image:Patella_post.jpg|Left patella - posterior aspect
Image:Gray345.png|Right knee-joint. Anterior view.
Image:Gray350.png|Sagittal section of right knee-joint.
Image:Gray351.png|Capsule of right knee-joint (distended). Lateral aspect.
Image:Gray1238.png|Front and medial aspect of right thigh.
Image:Gray1240.png|Lateral aspect of right leg.
</gallery>
==References==
<references/>
==External links==
* [http://www.kneeguru.co.uk/KNEEnotes/node/900 The KNEEguru - educational site packed with knee content with sections on the patella]
* {{SUNYAnatomyFigs|12|01|15}}
{{Bones of lower extremity}}
[[Category:Sesamoid bones]]
[[Category:Bones of pelvic limb]]
{{musculoskeletal-stub}}
[[ca:Patel·la]]
[[cs:Čéška]]
[[de:Kniescheibe]]
[[es:Rótula]]
[[eo:Patelo]]
[[fr:Patella (os)]]
[[id:Tulang lutut]]
[[it:Rotula (anatomia)]]
[[he:עצם הפיקה]]
[[la:Patella]]
[[lt:Girnelė]]
[[nl:Knieschijf]]
[[ja:膝蓋骨]]
[[no:Patella]]
[[pl:Rzepka]]
[[pt:Patela]]
[[sk:Jabĺčko]]
[[sl:Pogačica]]
[[fi:Polvilumpio]]
[[te:జానుఫలకము]]
[[th:กระดูกสะบ้า]]
[[uk:Надколінник]]