It can range from a very mild pink coloration of the skin, which disappears in a few hours after pressure is relieved on the area, to a very deep wound extending to and sometimes through a bone into internal organs. These ulcers, as well as other wound types, are classified in stages according to the severity of the wound.
All decubitus ulcers have a course of injury similar to a burn wound.
This blackened tissue is called eschar. The usual mechanism of forming a decubitus ulcer is from pressure. However it can also occur from friction by rubbing against something such as a bed sheet, cast, brace, etc., or from prolonged exposure to cold. Any area of tissue that lies just over a bone is much more likely to develop a decubitus ulcer. These areas include the spine, coccyx or tailbone, hips, heels, and elbows, to name a few.