Osteonecrosis of the knee.

We have described two entities of osteonecrosis-like syndromes about the knee. One involves the medial femoral condyle and may or may not be associated with radiolucent lesions and collapse of the femoral condyle. Treatment depends on identification of the size and location of the lesion. The other entity is an osteonecrosis-like lesion of the tibial plateau. It usually occurs medially and may not be associated with radiographic changes. However, increased uptake on a bone scan from the medial side of the knee, best noted on the lateral view, will identify these lesions. Once the condition is recognized, the patient should be treated conservatively until the clinical course is defined. It is important to recognize these clinical problems so that unnecessary surgery may be avoided.