Which statement correctly differentiates Stage 3 from Stage 4 pressure injuries?

Which statement correctly differentiates Stage 3 from Stage 4 pressure injuries?

• A. Stage 3 involves full-thickness skin loss with fat visible; Stage 4 involves bone, tendon, or muscle exposure
• B. Stage 3 is deeper than Stage 2
• C. Stage 3 involves only superficial skin redness
• D. Stage 3 involves full-thickness skin loss with fat visible; Stage 4 involves full-thickness tissue loss with bone, tendon, or muscle exposed

Answer: (D)

The key idea is how deep the injury goes and what tissues are exposed. Stage 3 is full-thickness skin loss with fat visible, meaning the wound goes through the skin into the subcutaneous tissue but does not expose bone, tendon, or muscle. Stage 4 goes even deeper, with full-thickness tissue loss and exposure of bone, tendon, or muscle, often with undermining or tunneling. This precise wording—Stage 3 as full-thickness skin loss with fat visible and Stage 4 as full-thickness tissue loss with bone, tendon, or muscle exposed—makes the difference clear.

The key idea is how deep the injury goes and what tissues are exposed. Stage 3 is full-thickness skin loss with fat visible, meaning the wound goes through the skin into the subcutaneous tissue but does not expose bone, tendon, or muscle. Stage 4 goes even deeper, with full-thickness tissue loss and exposure of bone, tendon, or muscle, often with undermining or tunneling. This precise wording—Stage 3 as full-thickness skin loss with fat visible and Stage 4 as full-thickness tissue loss with bone, tendon, or muscle exposed—makes the difference clear.