Computed tomography in osteochondritis dissecans of the patella

Osteochondritis dissecans is a disorder which rarely involves the patella. It must be differentiated from chondromalacia, lateral marginal fracture due to direct injury, medial facet osteochondral fracture secondary to traumatic lateral dislocation and a dorsal defect of the patella. I report a patient in whom computed tomography (CT) helped confirm the diagnosis. Although usually diagnosable from plain films, in difficult patients CT should be considered.