Stages of Pressure Sores: The Complete 6-Category EPUAP Guide 2026

There are six categories of pressure sore under the internationally recognised EPUAP/NPIAP classification system: Stage 1, Stage 2, Stage 3, Stage 4, Unstageable, and Deep Tissue Injury. A stage 3 or stage 4 pressure sore in a hospital or care home setting is almost always avoidable and frequently indicates that required preventive care was not delivered. Understanding the stages matters both for recognising deteriorating care and for understanding how negligence claims are valued.

Why the EPUAP/NPIAP Classification Matters

The European Pressure Ulcer Advisory Panel (EPUAP) and the National Pressure Injury Advisory Panel (NPIAP) developed a shared international classification system that is now the standard used across the NHS, care homes, and in medico-legal assessments. In negligence claims, the staging of a pressure ulcer determines the seriousness of the injury. A stage 4 ulcer does not appear overnight — it is the end point of a sequence of earlier-stage wounds that were not identified, not treated, or not escalated in time. NICE guideline CG179 sets the required standard of prevention, and failure to follow it is the central issue in most pressure ulcer claims. See the full NICE CG179 guideline.

How Pressure Sores Form — Before the Stages Begin

Pressure sores develop when sustained pressure on a part of the body cuts off blood supply to the skin and underlying tissue. Without oxygen, cells begin to die. A healthy person shifts position constantly — even during sleep — relieving pressure before damage can occur. Patients who are immobile, sedated, cognitively impaired, or paralysed cannot do this and are entirely dependent on staff to reposition them. Three additional mechanisms contribute alongside pressure: shear (tissue damage from sliding forces beneath intact skin); friction (surface abrasion during repositioning); and moisture (sweat, urine, or wound drainage weakening the skin barrier). Risk is formally assessed using tools such as the Waterlow score — an admission risk assessment is a requirement for any regulated care setting.

Stage 1 — Non-Blanching Erythema of Intact Skin

The skin is intact but shows persistent redness that does not fade when pressed. In darker skin tones, Stage 1 may appear as blue or purple discolouration. Other indicators include skin that feels warmer or cooler than surrounding area, localised pain or itching, and tissue that feels firmer or softer than normal. Stage 1 is a warning sign, not yet an open wound. With immediate repositioning and pressure relief, Stage 1 changes should reverse within 24 to 48 hours. Failure to respond to a documented Stage 1 finding — and the subsequent development of a Stage 2 or worse wound — is frequently the clearest evidence that the care plan was not followed.

Stage 2 — Partial Thickness Skin Loss

The skin is broken. A shallow open wound with a pink or red wound bed, or an intact or ruptured blister. There is no slough visible in the wound bed and no exposed fat, muscle, or bone. Stage 2 wounds are typically painful and require active wound management: appropriate dressings, pressure relief, and formal review of the care plan. Where a Stage 2 wound develops in a setting where the patient was already identified as at risk, the question is why the Stage 1 warning signs did not result in changes that prevented breakdown.

Stage 3 — Full Thickness Skin Loss

The wound extends through the full depth of the skin into the subcutaneous fat layer beneath. Visible fat may be present in the wound base. Slough or eschar may be present. Undermining and tunnelling of the wound edges may be seen. A Stage 3 pressure ulcer in a hospital or care home is a serious wound. In the absence of exceptional circumstances such as end-of-life care, a Stage 3 wound developing in a managed care setting almost always indicates that preventive measures were inadequate. These cases form the majority of successful pressure ulcer negligence claims.

Stage 4 — Full Thickness Tissue Loss With Exposed Structures

The wound extends to expose bone, tendon, muscle, or cartilage. Stage 4 wounds carry a very high risk of osteomyelitis (bone infection), which typically requires prolonged antibiotic treatment and sometimes surgical debridement or amputation. Sepsis is a serious risk. Stage 4 wounds can be fatal, particularly in elderly or frail patients. A Stage 4 pressure ulcer should never develop in a well-managed hospital or care home in a patient who does not have an underlying condition making tissue breakdown inevitable. See our guide to compensation for pressure ulcers in care homes.

Unstageable — Full Thickness, Obscured Base

The wound is full thickness in depth but the base is completely covered by slough or eschar, making it impossible to determine whether it is Stage 3 or Stage 4 without removing the covering tissue. The presence of sufficient slough or eschar to prevent staging indicates a wound of significant depth that has been present for some time. Failure to arrange debridement or specialist review of an Unstageable wound can itself constitute a breach of the required standard of care.

Deep Tissue Injury (DTI) — Suspected Deep Tissue Damage

Deep Tissue Injury presents as a localised area of persistent purple or maroon discolouration of intact skin, or a blood-filled blister, caused by pressure or shear forces damaging tissue beneath the skin surface. The overlying skin may be intact but the damage underneath is significant and may progress rapidly — sometimes to Stage 3 or Stage 4 within days. DTI is particularly relevant in negligence cases because it can develop under intact-looking skin, making it easy for care staff to miss or dismiss. Where a DTI is documented but not escalated, and subsequently progresses to Stage 4, the failure to respond to the early finding is central to the claim.

When the Stages of Pressure Sores Indicate Negligence

Not every pressure sore is negligent. A patient who is terminally ill, profoundly malnourished, or has end-stage vascular disease may develop pressure damage despite optimal care. Negligence is typically indicated when: no risk assessment was completed on admission; the care plan did not respond to a high-risk score; repositioning was not carried out or documented at the required frequency; pressure-redistributing equipment was not provided; Stage 1 changes were documented but not acted upon; a developing wound was not escalated; or treatment of an existing wound was inadequate, allowing deterioration. If you believe a loved one developed a stage 3 or stage 4 pressure ulcer because preventive care was inadequate, see our guide on whether you can claim pressure sore compensation.

Frequently Asked Questions