Osteonecrosis of the patella in patients with nontraumatic osteonecrosis of the femoral head: MRI findings in 60 patients.

We examined both knees in 60 patients with nontraumatic osteonecrosis of the femoral head with three-dimensional MRI. We found osteonecrosis of the patella in 9 patients (10 knees) and osteonecrosis of the femoral or tibial condyles/metaphyses in 35 patients (61 knees). In the patella, the necrosis was located in the proximal half and tended to develop in patients with other necrotic lesions in the knee.