1. In normal adult bone there is a variable amount of focal necrosis which occurs as part of the normal aging of the skeleton.
2. The extent of this necrosis increases with age and is related to the physiological aging of the vascular system and not to abnormalities of the osseous system.
3. Chronic peripheral vascular disease greatly increases the amount of necrosis of bone.
4. In the presence of severe chronic vascular insufficiency, there may be such massive necrosis as to include most of a long bone, such as the tibia, without any resulting changes in the clinical or roentgenographic picture.