Spontaneous osteonecrosis of the lateral femoral condyle of the knee: a report of 11 cases

BACKGROUND: Spontaneous osteonecrosis (SON) of the lateral femoral condyle of the knee joint is very rare and there have been only a few articles about this condition. MATERIALS: We reviewed data for 11 patients (7 men, 4 women) with unusual SON of the lateral femoral condyle of the knee. The average age of patients at onset was 61.9 years (range 47-76 years). No patient had underlying disease or had undergone steroid therapy, although one underwent lateral meniscectomy. RESULTS: According to Aglietti's radiographic classification, three patients had stage 1 disease, two had stage 2 disease, three had stage 3 disease, one had stage 4 disease, and two had stage 5 at first examination. The average alignment of affected limbs on standing was 5.9 degrees valgus (range 0 degrees -11 degrees ). Although the osteonecrotic lesion was seen on the lateral side, the mechanical axis passed the medial compartment in three patients. Six patients were treated conservatively and the remaining five required surgery, which consisted of lateral unicompartmental knee arthroplasties. CONCLUSION: The pathology of the necrosis of the lateral femoral condyle was considered to be different from that of the medial femoral condyle regarding clinical features, limb alignment, and radiographic findings.