Pressure ulcer

Pressure ulcers, also known as pressure sores, bed sores or pressure injuries, are damage to the skin and/or tissue that happen over a bony because of have a lot of pressure on it usually cause by a sitting or laying in bed for a long period of time. 
The most common sites are the skin overlying the sacrum, coccyx, heels, and hips. Other sites can be affected, such as the elbows, knees, ankles, back of shoulders, or the back of the cranium.