A condition of the hip in children, due to death and fragmentation of the epiphysis (or spongy extremity) of the head of the femur resulting from failure of its blood supply. The disease occurs in the 4–10 year age-group, with a peak between the ages of six and eight; it is ten times more common in boys than girls, and occurs on both sides in 10 per cent of cases. The initial sign is a lurching gait with a limp, accompanied by pain. Treatment consists of limiting aggressive sporting activity which may cause intact overlying CARTILAGE to loosen. Where there are no mechanical symptoms and MRI scanning shows that the cartilage is intact, only minor activity modification may be necessary – but for several months or even years. Any breach in the cartilage is dealt with at ARTHROSCOPY by fixing or trimming any loose flaps. Sometimes surgical treatment is advised, such as tenotomy or osteotomy. Eventually the disease burns itself out.