For certain conditions, the bone may be affected at the upper or lower end such as with avascular necrosis of the femur in the knee joint. When the site is at the joint, report the condition of the joint, not the bone.

When Avascular Necrosis happens at a joint, the joint surface will collapse.

Explanation:

Avascular necrosis (AVN) is a disorder resulting from a temporary or permanent loss of blood supply to the bone. Blood carries essential nutrients and oxygen to the bones. When the blood supply is disrupted (avascular), a break down (necrosis) to the bone tissues start to occur. The bone can be weakened by and eventually result in its collapse.

A collapse of the joint surface can happen if avascular necrosis happens near a joint, resulting in pain and inflammation (arthritis). AVN is also referred to as osteoradionecrosis, aseptic necrosis, or ischemic bone necrosis.

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