Full-thickness tissue loss with destruction, tissue necrosis, or damage to muscle, bone, or supporting structures. There may be sinus tracts, deep pockets of infection, tunneling, undermining, eschar (black scab-like material), or slough (tan, yellow, or green scab-like material).
Partial-thickness skin loss involving the epidermis and the dermis. The ulcer is visible and superficial and may appear as an abrasion, blister, or shallow crater. Edema persists, and the ulcer may become infected, possibly with pain and scant drainage.
Intact skin with an area of persistent, nonblanchable redness, typically over a bony prominence, that may feel warmer or cooler than the adjacent tissue. The tissue is swollen and has congestion, with possible discomfort at the site. With darker skin tones, the ulcer may appear blue or purple.
Full-thickness tissue loss with damage to or necrosis of subcutaneous tissue. The ulcer may extend down to, but not through, underlying fascia. The ulcer appears as a deep crater with or without undermining of adjacent tissue and without exposed muscle or bone. Drainage and infection are common.