Idiopathic osteonecrosis of the medial femoral condyle. Classification and treatment.

Idiopathic osteonecrosis of the medial femoral condyle is a well recognized cause of spontaneous, sudden onset of severe pain, usually at the anteromedial aspect of the knee joint. At the Department of Orthopaedic Surgery of the University of Ioannina, 105 knees in 101 patients were evaluated and treated for idiopathic osteonecrosis of the medial femoral condyle. The disease was found to follow a four-stage course, which consisted of a progression from no radiographic findings (Stage I), to a slight flattening of the medial condyle (Stage II), followed by the appearance of a radiolucent lesion (Stage III), and finally, articular cartilage collapse (Stage IV). Although Stages I and II potentially were reversible, Stages III and IV were associated with irreversible destruction of the subchondral bone and articular cartilage. Although bone scan is a nonspecific diagnostic modality, it was helpful in establishing diagnosis in the early stages of the disease. Conservative treatment was found appropriate for the first two stages, whereas surgical management was effective for patients with Stages III and IV. Specifically, osteotomy was useful for patients younger than 60 years of age with limited necrotic lesions, whereas unicompartmental arthroplasty was effective in older patients with more extensive lesions. Total knee arthroplasty can be reserved for cases where the disease has expanded to the lateral compartment.