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Transient lateral patellar dislocation complicated by osteochondral fragment

Case contributed by Chris O'Donnell
Diagnosis certain

Presentation

Dislocated patella yesterday, now knee is locking.

Patient Data

Age: 20 years
Gender: Male

Typical findings of lateral patellar dislocation but instead of the typical disruption to the medial patellar facet, the patella has cleaved off a large fragment of the lateral femoral condyle (large full thickness, osteochondral defect of the lateral femoral condylar articular surface).

Disruption to the medial patellar retinaculum and bone bruising on the inferomedial patella. Note the shallow trochlear groove.

Osteochondral loose body siting in the anterior joint space hence the clinical "locking".

Case Discussion

Typical findings of lateral patellar dislocation but instead of the typical disruption to the medial patellar facet, the patella has cleaved off a large fragment of the lateral femoral condyle. Surgeons will go in and try to salvage this fragment by anchor screw/pin reattachment.

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