Osteonecrosis of the knee. Medial and lateral involvement.

Osteonecrosis of the medial and lateral compartments of the right knee was observed in a 69-year-old man who had never been treated by steroids. Spontaneous osteonecrosis also developed in the left knee. He was treated by total knee arthroplasty. Lateral compartment osteonecrosis has not been reported previously, except in patients receiving steroid therapy.