A pressure ulcer occurs because

Answer 1

Bedsores (also called pressure sores or pressure ulcers) are injuries to skin and underlying tissue resulting from prolonged pressure on the skin. Bedsores most often develop on skin that covers bony areas of the body, such as the heels, ankles, hips and tailbone.
People most at risk of bedsores are those with a medical condition that limits their ability to change positions, requires them to use a wheelchair or confines them to a bed for a long time.