Nonblanchable erythema of intact skin (skin remains erythematous under pressure). Can be superficial or represent deep tissue damage. Persons with dark skin can be difficult to evaluate for this stage.
Partial-thickness loss involving the epidermis or dermis. No subcutaneous tissue is visible. Lesions may look like an abrasion or a shallow depression.
Full-thickness loss. Subcutaneous tissue is damaged or necrotic and invisible in the wound. May have undermining of the skin surrounding the wound. The fascia of underlying tissue is intact.
Extend into bone or muscle. Ulcers are associated with extensive damage and necrosis. Prosthetic joints or other implanted foreign bodies may be visible in the wound. Undermining or sinus tract formation is often present.