Pressure ulcers are classified by increasing severity in stages 1 through 4, the National Pressure Ulcer Advisory Panel explains. Stage 1 is typically limited to outer skin damage, while the subsequent stages exhibit greater degrees of underlying tissue damage and exposure of interior fat, muscle and bone. Physicians use two additional classifications to categorize wounds that are difficult to stage or suspected of containing deep tissue damage.
Sores classified as stage 1 have no skin breaks, but they may have a red appearance or a texture that differs from the surrounding skin, WebMD states. Briefly touching the wound does not cause blanching, or loss of color, and the skin may feel warm. In stage 2, the wound is tender and painful and appears open, blistered or lesioned. Some skin may be irreparable or dead. In stage 3, tissue damage continues deeper into the skin, causing a craterous shape that may expose underlying fat.
By stage 4, ulcers have extensive damage to underlying connective tissues or supporting structures, the National Pressure Ulcer Advisory Panel notes. Tendons, muscles or bones may be exposed, and dead tissue overwhelms the affected area. Doctors may classify an ulcer as a suspected deep tissue injury if the depth of damage is unknown. The wound is typically unbroken or blistered with purple discoloration and mushy or firm skin. Unstageable ulcers also have an unknown depth, and doctors must remove substantial dead tissue to determine whether the wound is at stage 3 or 4.