Perthes’s disease occurs most commonly in the age range of four to eight years, it is more common in boys than in girls by a ratio 5:1. The incidence ofbilaterality has been reported as 10 to 20%. The aetiology of the diseaseremains unkown, although many theories have been proposed, amongthem are trauma, inflammation, infection. In Perthes disease, there isinitial ischaemic episode due to interruption of the circulation in lateralepiphyseal vessels. Revascularization follows, but recurrent obstructionto revascularization occur due to subchondral fracture.