Legg-Calves-Perthes disease is a condition that often begins in childhood. It occurs when part of the hip joint does not receive an adequate amount of blood supply. When this happens, bone cells begin to die, and the joint deteriorates. As a result, a person may experience pain and gait problems. It can also increase the risk of a person developing osteoarthritis later in life. Legg-Calves-Perthes disease is also known as idiopathic osteonecrosis, ischemic necrosis of the hip, coxa plana, osteochondritis, or avascular necrosis of the femoral head. It is estimated that about one in every 1,200 children have Legg-Calves-Perthes disease.