Pressure injuries (bed sores) are an injury to the skin and underlying tissue. They can range from mild reddening of the skin to severe tissue damage-and sometimes infection-that extends into muscle and bone. Pressure injuries are described in four stages:
Stage 1 sores are not open wounds. The skin may be painful, but it has no breaks or tears. The skin appears reddened and does not blanch (lose color briefly when you press your finger on it and then remove your finger). In a dark-skinned person, the area may appear to be a different color than the surrounding skin, but it may not look red. Skin temperature is often warmer. And the stage 1 sore can feel either firmer or softer than the area around it.
At stage 2, the skin breaks open and wears away or forms an ulcer, which is usually tender and painful. The sore expands into deeper layers of the skin. It can look like a scrape (abrasion), blister, or a shallow crater in the skin. Sometimes this stage looks like a blister filled with clear fluid. At this stage, some skin may be damaged beyond repair or may die.
During stage 3, the sore gets worse and extends into the tissue beneath the skin, forming a small crater. Fat may show in the sore, but not muscle, tendon, or bone.
At stage 4, the pressure injury is very deep, reaching into muscle and bone and causing extensive damage. Damage to deeper tissues, tendons, and joints may occur.