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Patella
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Contents
Description
- General
- Largest sesamoid bone in the body
- Embedded in quadriceps tendon
- Osseous features
- Medial and lateral facets, lateral is large
- Separated by vertical ridge
- Extensor Mechanism
- The Quadriceps Tendon inserts on proximal pole of patella
- Majority of patella is encased by the tendon
- Inferior pole transitions to Patellar Tendon where it inserts on the Tibial Tubercle
- Patellar Retinaculum
- NEEDS TO BE UPDATED
- Cartilage
- Posterior surface covered with thick articular cartilage (up to 1 cm)
- Ligaments
- Medial Patellofemoral Ligament
- Lateral Patellofemoral Ligament
- Embriology
- Ossifies between ages 4 and 7
- Although most individuals have a single ossification center, up to 23% of folks have 2 or 3 ossification centers
- 2% of individuals do not ossify at these centers resulting in bipartite or tripartite patella
- In 50% of cases this is seen bilaterally
- Wiberg subtypes[1]
- Type I: medial and lateral facets are approximately equal
- Type II & Type III: medial facet becomes steadily smaller
Actions
- Functions as a lever arm during extension[2]
- Augments quadriceps and extensor mechanism
- Augments the lever arm by up to 30% at full extension[3]
- Knee Flexion
- Located in the groove of the femoral trochlea acting primarily as a link between the quadriceps muscle and the proximal tibia
- Most pressure occurs at 45°-60° flexion[4]
- Resistance to flexion[5]
- Converts tensile forces into compression forces
- Decelerates knee flexion in particular during walking down stairs or downhill
- Sometimes termed “patella femoral joint reaction (PFJR)”
Vascular Supply
- Branches of the following arteries form anastomotic ring
- Descending genicular
- Superior medial and lateral genicular
- Inferior medial and lateral genicular
- Anterior genicular
Innervation
- Medial and lateral patellar nerves
Clinical Significance
See Also
References
- ↑ Wiberg G. Roentgenographs and anatomic studies on the femoropatellar joint: with special reference to chondromalacia patellae. Acta Orthop Scand. 1941;12:319–410.
- ↑ colaro J, Bernstein J, Ahn J. Patellar fractures. Clin Orthop Relat Res. 2011 Apr;469(4):1213–1215.
- ↑ Kaufer H. Mechanical function of the patella. J Bone Joint Surg Am. 1971 Dec;53(8):1551–1560.
- ↑ Goldstein SA, Coale E, Weiss AP, Grossnickle M, Meller B, Matthews LS. Patellar surface strain. J Orthop Res. 1986;4(3):372–377.
- ↑ Hungerford DS, Barry M. Biomechanics of the patellofemoral joint. Clin Orthop Relat Res. 1979 Oct;(144):9–15.