Pressure ulcers are categorized into four stages, based on their severity:
Stage 1: Reddened skin that does not blanch (turn white) when pressed. The skin may be painful, but there are no open wounds. Stage 2: Partial-thickness skin loss presenting as a shallow open ulcer with a red-pink wound bed, without slough. It may also present as an intact or open/ruptured serum-filled blister. Stage 3: Full-thickness tissue loss. Subcutaneous fat may be visible, but bone, tendon, or muscle are not exposed. Stage 4: Full-thickness tissue loss with exposed bone, tendon, or muscle. Slough or eschar may be present. Undermining and tunneling often occur.
