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Patella

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(Redirected from Inferior patellar)

Description

Anterior view of a right knee. The patellofemoral articulation is composed of the convex patella within the trochlear groove of the femur. Major components of the extensor mechanism include the quadriceps tendon proximally and the patellar ligament distally.[1]
Anterior and posterior views of the patella with the anterior view depicting regions of the patella and the posterior view showing the facets and patellar ridge of the articular surface[2]
Vascular supply of the patella shown from the (a) anterior aspect and (b) posterior aspect[1]
Normal sunrise view of the patella and patellofemoral joint

Name

  • Patella
  • Kneecap

General

Osseous features

  • Medial and lateral facets, lateral is large
  • Separated by vertical ridge

Extensor Mechanism of the Knee

Patellar Retinaculum/ Ligaments

Cartilage

  • Posterior surface covered with thick articular cartilage (up to 1 cm)
  • Articulates with distal femur in the facies patellaris to form patellofemoral joint

Embryology

  • 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[3]

  • 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[4]
    • Augments quadriceps and extensor mechanism
    • Augments the lever arm by up to 30% at full extension[5]
  • 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[6]
  • Resistance to flexion[7]
    • 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 the Genicular Anastomosis
    • Descending genicular
    • Superior medial and lateral genicular
    • Inferior medial and lateral genicular
    • Anterior genicular

Innervation

Clinical Significance

See Also

References

  1. ↑ 1.0 1.1 Fox, Alice JS, Florian Wanivenhaus, and Scott A. Rodeo. "The basic science of the patella: structure, composition, and function." The journal of knee surgery 25.02 (2012): 127-142.
  2. ↑ Wheatley, Mitchell GA, Michael J. Rainbow, and Allison L. Clouthier. "Patellofemoral mechanics: a review of pathomechanics and research approaches." Current reviews in musculoskeletal medicine 13 (2020): 326-337.
  3. ↑ Wiberg G. Roentgenographs and anatomic studies on the femoropatellar joint: with special reference to chondromalacia patellae. Acta Orthop Scand. 1941;12:319–410.
  4. ↑ colaro J, Bernstein J, Ahn J. Patellar fractures. Clin Orthop Relat Res. 2011 Apr;469(4):1213–1215.
  5. ↑ Kaufer H. Mechanical function of the patella. J Bone Joint Surg Am. 1971 Dec;53(8):1551–1560.
  6. ↑ Goldstein SA, Coale E, Weiss AP, Grossnickle M, Meller B, Matthews LS. Patellar surface strain. J Orthop Res. 1986;4(3):372–377.
  7. ↑ Hungerford DS, Barry M. Biomechanics of the patellofemoral joint. Clin Orthop Relat Res. 1979 Oct;(144):9–15.
Created by:
John Kiel on 18 October 2020 01:23:05
Authors:
Last edited:
20 March 2025 16:46:23
Category:
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