The origin of this pathology is not always clear and is defined as idiopathic, when arises spontaneously and the causes are unknown. It may also due to venous thrombosis, hypertension, chronic use of medications (e.g. corticosteroids), treatments (radiation) and preexisting autoimmune or blood conditions.
Other causes leading to avascular necrosis of the hip may depend on different forms of injuries while others arise from intrinsic vascular changes compromising blood flow to the femoral head.
Trauma includes fractures of femoral head 75-100%, basicervical or femoral head base 50%, cervico-trochanteric head-trochanter 25%
Hip dislocation (2-40%); higher risk with severe displacement and incorrect reduction.