Traumatic and nontraumatic causes can lead to an insult to the blood supply of the joint. The ischemia causes death of osteocytes and bone marrow that leads to<unk>  and eventual collapse of the dead segment.
Estimate of 10,000 to 20,000 new cases per year
Responsible for about 10% of all total hip replacements
Patients typically diagnosed before 40 years of age
Traumatic causes
Femoral neck fracture/dislocation
Non-traumatic causes
Use of corticosteroids, alcohol, tobacco
Systemic lupus erythematosus
Sickle cell disease
Chronic Kidney Disease
Pancreatitis
Radiation therapy
HIV
Caisson Disease (aka Dysbarism)
Legg-Calve-Perthes disease
Idiopathic
Avascular necrosis of hip
Acute Trauma
Hip bursitis
Femur fracture
Ankle dislocation
Proximal
Knee dislocation
Intracapsular