The sad truth is that very little is really known about the disease, AVN. Medical researchers and doctors have been able to draw some correlations to possible risk factors though. The top causes of AVN are thought to be steroid medications, injury to bone, alcohol use, and some other related diseases.

Steroid Medications
Oral steroids, such as Prednisone, and injected corticosteriods both have been strongly linked as likely causes of AVN. The assertion is that steroid use can interfere with the body's ability to break down fatty substances in the blood stream. These fatty deposits may then cause blockages in bone blood vessels resulting in constriction and death of the affected bone site. The degree of risk present in the use of steroid medications is a hotly debated topic. Some sides claim the risk of steroid medication use to be very low.  On the other hand, other groups assert that over 70% of all AVN patients took steroid medications before onset of the disease.

Injury
Another known correlation to AVN is trauma-related injury to the bone. Significant blunt force trauma, stress, fracture, or even compression are thought to significantly increase the risk of developing AVN. Certain types of car accidents, for example, can inflict enough blunt force trauma to damage the blood vessles inside of bone, cutting off the blood supply and resulting in AVN. Also, studies show that up to 20% of people that dislocate a hip go on to develop AVN.

Alcohol Use
Excessive alcohol use is thought to be another very significant cause of AVN. The underlying theory is that excessive alcohol use disrupts the body's natural ability to breakdown fatty substances in the blood. These fatty substances then lodge in narrowed blood vessles in bone restricting blood supply and causing AVN.

Other Potential Factors
Other medical conditions and medical treatments are known to have correlations to AVN as well. Some of the top associated risks are Gaucher's disease, radiation therapy, chemotherapy, decompression disease, and other blood disorders.