Spontaneous osteonecrosis of the medial tibial plateau.

Spontaneous osteonecrosis (ON) of the medial tibial plateau was diagnosed in 15 elderly patients (21 knees). The onset was characterized by sudden severe medial knee pain, usually with an effusion. Radiographic changes suggestive of ON occurred medial to the weight bearing area of the medial tibial plateau in 9 knees and were normal in 12. The disease entity was documented most clearly by intense radionuclide bone uptake in the medial tibial plateau in all knees. It could be distinguished clinically and radiologically from medial femoral ON, tibial stress fractures and primary osteoarthritis (OA). Tibial ON did not appear to accelerate the development or progression of OA of the knee and most patients were better in less than 1 year.