patella
American Heritage Dictionary:
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pa·tel·la
(pə-tĕl'ə) 
n., pl., -tel·lae (-tĕl'ē).
n., pl., -tel·lae (-tĕl'ē).
- A flat triangular bone located at the front of the knee joint. Also called kneecap.
- A dish-shaped anatomical formation.
- A pan or dish in ancient Rome.
[Latin, diminutive of patina, plate, pan. See paten.]
patellar pa·tel'lar or pa·tel'late (-tĕl'ĭt, -āt') adj.
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A small lens-shaped sesamoid bone encased in the patellar tendon at the front of the knee. The patella protects the knee-joint anteriorly and improves the leverage of the knee extensor muscles by as much as 50%. It also increases the area of contact between the patellar tendon and the femur decreasing mechanical stress on the patellofemoral joint. The patella is poorly nourished and poorly protected, consequently it is susceptible to injury.
Saunders Veterinary Dictionary:
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patella
Pl. patellae [L.] a large sesamoid bone at the femorotibial joint.
- p. cubiti — an anomalous sesamoid over the extensor aspect of the elbow.
Random House Word Menu:
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categories related to 'patella'
- Skeleton - patella: knee bone
- Basins, Ladles, Cups, and Pots - patella: small pan or vase (ancient Rome)
Wikipedia on Answers.com:
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Patella
For other uses, see Patella (disambiguation).
- Kneecap redirects here. Or see NECAP or wiktionary:kneecap.
| Bone: Patella | |
|---|---|
 |
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| Right knee | |
| Latin | patella |
| 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 anterior articular surface of the knee joint. It is the largest sesamoid bone in the human body.
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Contents
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Structure
The patella is roughly triangular in shape with its base facing proximally (towards the torso) and its tip (apex patellae) facing distally (towards the feet). Its anterior and posterior surfaces are joined laterally (left/right) by a thinner margin and medially (towards centre) by a thicker margin.[1]
Anterior surface
The anterior surface can be divided into three parts:[1]
- The upper third is coarse, flattened, and rough; it serves for the attachment of the tendon of the quadriceps and often has exostoses.
- The middle third has numerous vascular canaliculi.
- The lower third includes the distal apex which serves as the origin of the patellar ligament.
Posterior surface
The posterior surface is divided into two parts.[1]
The upper three-quarters articulates with the femur and is subdivided into a medial and a lateral facet by a vertical ledge which varies in shape. Four main types of articular surface can be distinguished:
- Most commonly the medial articular surface is smaller than the lateral.
- Sometimes both articular surfaces are virtually equal in size.
- Occasionally, the medial surface is hypoplastic or
- the central ledge is only indicated.
In the adult the articular surface is about 12 cm2 (1.9 sq in) and covered by cartilage, which can reach a maximal thickness of 6 mm (0.24 in) in the centre at about 30 years of age.
The lower part of the posterior surface has vascular canaliculi filled and is filled by fatty tissue, the infrapatellar fat pad.
Variants
Emarginations (i.e. patella emarginata, a "missing piece") are common laterally on the proximal edge.[1] Bipartite patellas are the result of an ossification of a second cartilaginous layer at the location of an emargination. Previously, bipartite patellas were explained as the failure of several ossification centres to fuse, but this idea has been rejected. Partite patellas occur almost exclusively in men. Tripartite and even multipartite patellas occur.
Muscles
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.
Function
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.
Ossification
In the patella an ossification centre develops between the ages 3–6 years.[1]
Evolutionary variation
The patella has convergently evolved in placental mammals and birds; most marsupials have only rudimentary, non-ossified patellae although a few species possess a bony patella.[2] A patella is also present in the living monotremes, the platypus and the echidna. In more primitive tetrapods, including living amphibians and most reptiles (except some Lepidosaurs), the muscle tendons from the upper leg are attached directly to the tibia, and a patella is not present.[3]
Dislocation
Main article: Patellar dislocation
Patellar dislocations occur with significant regularity, particular in young female athletes.[4] It involves the patella sliding out of its position on the knee, most often laterally, and may be associated with extremely intense pain and swelling.[5] The patella can be tracked back into the groove with an extension of the leg, and therefore sometimes returns into the proper position on its own.[5]
See also
Additional images
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References
- ^ a b c d e Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.). Thieme. p. 194. ISBN 3-13-533305-1.
- ^ Herzmark MH (1938). "The Evolution of the Knee Joint". J Bone Joint Surg Am 20 (1): 77–84. http://www.ejbjs.org/cgi/reprint/20/1/77.pdf. Retrieved 2007-11-17.
- ^ Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. p. 205. ISBN 0-03-910284-X.
- ^ Palmu, S.; Kallio, P.E.; Donell, S.T.; Helenius, I.; Nietosvaara, Y. (2008). "Acute patellar dislocation in children and adolescents: A randomized clinical trial". Journal of Bone and Joint Surgery 90 (3): 463–470. doi:10.2106/JBJS.G.00072. PMID 18310694.
- ^ a b Dath, R.; Chakravarthy, J.; Porter, K.M. (2006). "Patella Dislocations". Trauma 8: 5–11. doi:10.1191/1460408606ta353ra.
External links
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Wikimedia Commons has media related to: Patella |
- "Patella overview". The KNEEguru. http://www.kneeguru.co.uk/KNEEnotes/node/1789. Retrieved March 2010.
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This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Translations:
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Patella
Dansk (Danish)
n. - lille skål, knæskal
Deutsch (German)
n. - Kniescheibe
Ελληνική (Greek)
n. - γαβαθάκι, (ανατ.) επιγονατίδα
Português (Portuguese)
n. - patela (f) (Med.)
Svenska (Swedish)
n. - knäskål
中文（简体）(Chinese (Simplified))
膝盖骨
中文（繁體）(Chinese (Traditional))
n. - 膝蓋骨
한국어 (Korean)
n. - 슬개골, 종지뼈, 작은 접시
العربيه (Arabic)
(الاسم) رضفه, داغضه, صابونه الركبه
עברית (Hebrew)
n. - פיקת-הברך
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American Heritage Dictionary
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
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Oxford Dictionary of Sports Science & Medicine
The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.
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Saunders Veterinary Dictionary
Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.
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Random House Word Menu
© 2010 Write Brothers Inc. Word Menu is a registered trademark of the Estate of Stephen Glazier.
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Wikipedia on Answers.com
This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Patella.
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