Findings: STIR coronal images of the knee demonstrate a bone bruise within the lateral femoral condyle as well as the inferior aspect of the patella. In addition, axial turbo spin echo T2 weighted image of the knee demonstrates a disruption of the medial patellar surface with an area of low signal intensity most consistent with an osteochondral fragment.

Diagnosis: Lateral patellar dislocation with subsequent recapture.

Discussion: Dislocations of the patella are usually lateral. Dislocations are easily diagnosed on a plain radiograph. These MR images demonstrate the constellation of findings seen following relocation of a lateral patellar dislocation. Specifically, there is cortical disruption of the medial facet of the patella. In addition, a lateral femoral condylar bone bruise is identified. A joint effusion is also seen. Incidental note is made of a Baker's cyst.

Reference:
Greenspan A.Orthopedic Radiology: A Practical Approach.
Lippincott, Williams & Wilkins, Philadelphia; 2000:248-249.

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