Irreducible lateral dislocation of patella with rotation

Acute lateral patellar dislocation is relatively common in younger age group and most likely caused by indirect trauma. About 10% of acute patella dislocations are the result of a direct blow to the medial side. We report a case of irreducible lateral patellar dislocation which is of exceptional interest in that lateral patellar dislocation (extra-articular) occurred in comparatively older age group with arthritic knee, there was no direct trauma involved and it was associated with some rotation along long axis, impaction of patella on lateral femoral condyle and was locked underneath osteophytic ridge of lateral femoral condyle, which needed open reduction. This is a very rare injury, first of its kind being reported in Australia.