The National Pressure Ulcer Advisory Panel-European Pressure Ulcer Advisory Panel classification system for pressure ulcers8
| Stage | Description |
| I | Non-blanching erythema of intact skin. Differential diagnoses include dermatitis, neurogenic ulcer and deep tissue pressure injury. |
| II | Partial thickness skin loss including epidermis. Dermis is exposed but intact, or there may be ruptured blisters. |
| III | Full-thickness skin loss including epidermis and dermis. Adipose tissue may be visible and granulation tissue can be seen. |
| IV | Full-thickness skin and tissue loss which exposes underlying muscle, tendon, bone or ligament. |
| Unstageable | Full-thickness with tissue loss, the extent of which cannot be assessed due to slough or eschar. |
| Deep tissue injury | Intact skin with persistent deep red or maroon discolouration. |