Transient patellar dislocation

Case contributed by Dr Mohammad A. ElBeialy

Presentation

15 years old girl with post-traumatic anterior knee pain.

Patient Data

Age: 15 years
MRI

 

  • the medial patellar facet and the lateral femoral condyle show osseous bruising with detached small bone fragments as well as marrow oedema signal with low T1 and high PDFS / STIR signal intensity.     
  • the medial patellar retinaculum shows focal partial thickness tear with oedema signal intensity within and around.
  • moderate haemorrhagic joint effusion with fat-fluid level (lipohaemarthrosis).
  • no meniscal tear.

     

  • intact cruciates and collateral ligaments as well as lateral patellar retinaculum, quadriceps and patellar tendons.

     

  • normal signal and girth of the peri-articular musculature with preserved intermuscular fat planes.

     

CT

 

  • transient patellar dislocation with osseous bruising and fracture of the medial patellar facet as well as the lateral femoral condyle with focal partial thickness tear of the medial patellar retinaculum.

     

  • moderate haemorrhagic joint effusion (lipo-haemoarthrosis).

     

Case Discussion

The triad of bone contusions of the anterior lateral femoral condyle and medial patella as well as partial or complete thickness tear of the medial patellar retinaculum is diagnostic of transient patellar dislocation.

 

 

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Case information

rID: 26174
Case created: 3rd Dec 2013
Last edited: 16th Dec 2015
Inclusion in quiz mode: Included

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