Osteopetrosis is a relatively rare disease characterized by increased density of the bones and disturbance of bone modelling. As a condition of hip joint associated with osteopetrosis, femoral neck fracture, osteoarthritis and coxa vara were reported. We experienced an unusual complication of bilateral avascular necrosis of the femoral heads with this diease. A 12-year-old boy was admitted to our institution, suffering from limping. His hips had flexion and internal rotation contracture. Radiographical changes of his bones showed typical osteopetrosis and in his hip joints, flattened femoral head and loss of epiphyseal height were found. In histlogical findings, the necrotic bone existed surrounding the fibrous tissue. These findings suggested those of Legg-Calve-Perthes disease.
