Lateral patellar dislocation

Lateral patellar dislocation refers to lateral displacement followed by dislocation of patella due to disruptive changes to the medial patellar retinaculum.

Patellar dislocation accounts for ~3% of all knee injuries and is commonly seen in those individuals who participate in sport activities.

Patella dislocation most commonly results from a twisting motion, with the knee in flexion and the femur rotating internally on a fixed foot (valgus-flexion-external rotation) 1.

  • lateral displacement of patella noted on skyline projection
  • joint effusion
  • sliver sign

The following features are noted:

  • medial retinacular abnormalities (ranging from strain to complete disruption ) with adjacent periligamentous edema and haemorrhage
  • lateral displacement of patella
  • medial patellar contusion +/- corresponding lateral femoral condyle contusion
  • joint effusion

The presence of an abnormal medial retinaculum should suggest the diagnosis of transient lateral patellar dislocation 1.

  • acute ACL tear: no medial patella contusion in this injury
  • direct trauma to lateral knee: normally no patellar contusion 4
Knee pathology

The knee is a complex synovial joint that can be affected by a range of pathologies:

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Article information

rID: 27273
Synonyms or Alternate Spellings:
  • Transient lateral patellar dislocation

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Cases and figures

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    Case 8: relocated
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    Case 9: torn medial patellar retinaculum
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