Causes
There are many theories about what causes avascular necrosis. Proposed risk factors include, chemotherapy, alcoholism, excessive steroid use, post trauma, caisson disease (decompression sickness), vascular compression, hypertension, vasculitis, arterial embolism and thrombosis, damage from radiation, bisphosphonates (particularly the mandible), sickle cell anaemia, Gaucher's Disease, and deep diving. In some cases it is idiopathic (no cause is found). Rheumatoid arthritis and lupus are also common causes of AVN. Prolonged, repeated exposure to high pressures (as experienced by commercial and military divers) has been linked to AVN, though the relationship is not well-understood.
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