Lateral patellar dislocation

Case contributed by Dr Andrew Lawson

Presentation

Knee pain

Patient Data

Age: 18
Gender: Male
Modality: MRI

There is marrow oedema within the anterolateral aspect of the lateral femoral condyle, and medial patellar facet. This pattern of bone contusion is consistent with a transient lateral patellar dislocation injury. There remains minor lateral subluxation of the patella. 

There are 2 fracture fragments adjacent to the lateral femoral condyle, which measure the 12 x 5mm and 19 x 4mm. The more superior fracture fragments is horizontally flipped. There are also 2 osteochondral fracture fragments adjacent to the medial patellar facet, which measure 5 x 10mm and 4 x 7mm. 

There is associated high-grade partial thickness tear of medial patellofemoral ligament at its patellar insertion. There are some intact residual fibres noted. No patella alta. No clear evidence of trochlea dysplasia. There is high signal and thickening of the patella tendon insertion on the tibial tuberosity. 

There is associated bony spurring of the tibial tuberosity. The medial meniscus and MCL are intact. The lateral meniscus, iliotibial band, fibular collateral ligament, biceps femoris tendon and popliteus tendon are intact. Moderate knee joint effusion.

Case Discussion

Transient lateral patellar dislocation injury, with fractures of the anterolateral aspect of the lateral femoral condyle and osteochondral fractures of the medial patellar facet. No patellar alta or evidence of significant trochlear dysplasia. 

Patellar tendon insertion high signal and thickening is likely unrelated to the acute injury and is more likely secondary to chronic avulsion injury Osgood-Schlatter's disease.

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Case Information

rID: 25852
Case created: 12th Nov 2013
Last edited: 29th Sep 2015
Inclusion in quiz mode: Included

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