The treatment of spontaneous osteonecrosis of the knee by high tibial osteotomy with and without bone-grafting or drilling of the lesion.

High tibial osteotomy to correct a varus or valgus deformity was performed on thirty-seven knees (thirty-six patients) with spontaneous osteonecrosis of the femoral condyle (thirty-five medial and two lateral). Drilling or bone-grafting of the necrotic lesion was done concomitantly with the osteotomy in twenty-three knees. Follow-up periods ranged from two years to eight years and six months. Preoperative pain was relieved and walking ability was improved in thirty-five knees. The clinical results, as rated by a knee score, were better in those knees with osteonecrosis of the medial femoral condyle and a postoperative femorotibial angle (as measured on a standing roentgenogram) ranging from 164 to 173 degrees (7 to 16 degrees of valgus angulation). Postoperatively in seventeen knees. Roentgenographic improvement was greater in those knees in which tibial osteotomy was performed concomitantly with bone-grafting or drilling. Postoperative arthrotomy in eight knees showed that the necrotic lesion was covered with a white layer of fibrocartilage in three of the four knees that had had osteotomy more than one and one-half years previously.