Which stage involves full-thickness tissue loss with exposed bone, muscle, or tendon?

• A. Stage 1
• B. Stage 3
• C. Stage 4
• D. Unstageable

Answer: (C)

Full-thickness tissue loss with exposed bone, muscle, or tendon is the deepest level of a pressure injury. At this stage the wound has penetrated through the dermis and subcutaneous tissue, revealing underlying structures such as bone, tendon, or muscle, and it may also show slough or eschar and possibly undermining or tunneling. This is Stage IV, the most severe documented stage for pressure injuries.

Stage III, by contrast, involves full-thickness loss but does not expose bone, tendon, or muscle; subcutaneous tissue may be visible. Unstageable describes a wound whose true depth cannot be determined because it is obscured by slough or eschar. Stage I is non-blanchable redness of intact skin.