Pressure Ulcer Staging System
Pressure ulcers are classified into four distinct stages (I through IV) based on the depth of tissue damage, with two additional categories for unstageable wounds and suspected deep tissue injury. 1, 2
Stage I: Non-Blanchable Erythema
- Intact skin with localized area of non-blanchable redness, usually over a bony prominence
- The area may be painful, firm, soft, warmer, or cooler compared to adjacent tissue
- May be difficult to detect in patients with darker skin tones
- This represents the earliest warning sign and is completely reversible with appropriate intervention 2, 3
Stage II: Partial-Thickness Skin Loss
- Partial-thickness loss of dermis presenting as a shallow open ulcer with a red-pink wound bed
- May also present as an intact or ruptured serum-filled blister
- No slough or eschar present
- Appears as a shiny or dry shallow ulcer without bruising 2, 3
Stage III: Full-Thickness Skin Loss
- Full-thickness tissue loss where subcutaneous fat may be visible
- Bone, tendon, and muscle are NOT exposed
- Slough may be present but does not obscure the depth of tissue loss
- May include undermining and tunneling
- Depth varies by anatomical location—areas with significant adiposity can develop extremely deep Stage III ulcers 2, 3
Stage IV: Full-Thickness Tissue Loss with Exposed Bone/Muscle/Tendon
- Full-thickness tissue loss with exposed bone, tendon, or muscle
- Slough or eschar may be present on some parts of the wound bed
- Often includes undermining and tunneling
- Depth varies by anatomical location
- Can extend into muscle and supporting structures, making osteomyelitis a significant risk
- These ulcers carry the highest morbidity and mortality risk and are associated with substantially increased treatment costs 3
Additional Categories
Unstageable/Unclassified
- Full-thickness tissue loss where the base of the ulcer is covered by slough and/or eschar in the wound bed, obscuring true depth
- Cannot be staged until enough slough/eschar is removed to expose the base of the wound 1
Suspected Deep Tissue Injury
- Purple or maroon localized area of discolored intact skin or blood-filled blister
- Results from damage to underlying soft tissue from pressure and/or shear
- May be preceded by tissue that is painful, firm, mushy, boggy, warmer, or cooler compared to adjacent tissue
- May evolve rapidly to reveal the actual extent of tissue injury or resolve without tissue loss 1
Critical Clinical Implications
The progression from Stage I to Stage IV represents exponentially increasing morbidity, mortality, and cost. Between 1990 and 2001, pressure ulcers were listed as the underlying cause of death in over 21,000 persons 4. Treatment costs for Stage IV ulcers range from $37,800 to $70,000 per case, with over 50% of the $26.8 billion annual cost attributed to treating Stage III and IV injuries 4, 5.
Early recognition and aggressive treatment of Stage I and II ulcers can prevent nearly all Stage IV ulcers, dramatically reducing complications and costs 3. The most commonly affected anatomical sites are the sacrum, heels, and hips, with Stage I (43.5%) and Stage II (28.0%) being the most frequently occurring stages 6.
Key Pitfall to Avoid
Do not underestimate Stage I ulcers—they represent a critical intervention window. Patients with limited mobility should undergo daily skin assessment, as the presence of non-blanchable erythema demands immediate implementation of pressure relief measures to prevent progression 3.