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Pressure Ulcer Stages: NPIAP Classification Explained
Pressure ulcers — now called "pressure injuries" by the National Pressure Injury Advisory Panel (NPIAP) — are graded by depth and tissue involvement. The NPIAP system has four numbered stages plus two special categories: Unstageable (full-thickness loss obscured by slough or eschar) and Deep Tissue Pressure Injury (DTPI), which is intact or non-intact skin overlying damaged underlying tissue. Earlier stages (1, 2, and DTPI) can often be reversed with prompt offloading and skin care. Full-thickness injuries (3, 4, Unstageable) take much longer to heal and carry higher infection risk. AHRQ identifies pressure injuries as largely preventable with proper turning, support surfaces, and nutrition.
Educational reference · Updated 2026-04-27
| Aspect | Early-Stage Injuries | Full-Thickness Injuries |
|---|---|---|
| Stages included | Stage 1, Stage 2, Deep Tissue Pressure Injury (DTPI) | Stage 3, Stage 4, Unstageable |
| Skin integrity | Intact (Stage 1, DTPI) or partial-thickness loss (Stage 2) | Full-thickness loss; muscle/bone may be visible |
| Visible structures | Stage 1: erythema; Stage 2: shallow dermis or open blister | Stage 3: subcutaneous fat; Stage 4: muscle, tendon, or bone |
| Reversibility | Often reversible with offloading and skin care | Healing measured in weeks to months; surgery sometimes needed |
| Infection risk | Lower; cellulitis possible but uncommon | Higher; abscess, osteomyelitis, sepsis possible |
| Typical management | Pressure redistribution, moisturization, protective dressings | Debridement, advanced dressings, NPWT, possible surgical closure |
Why pressure injuries are staged
Staging guides treatment, predicts healing time, and standardizes communication between settings (hospital, skilled nursing, home health, wound clinic). NPIAP, the U.S. authority on pressure injury terminology, updated the staging system in 2016 — replacing "pressure ulcer" with "pressure injury" because Stage 1 and DTPI involve intact skin (so "ulcer" was inaccurate). AHRQ identifies pressure injuries as a leading preventable harm in inpatient care and publishes a prevention toolkit emphasizing risk assessment (Braden Scale), repositioning schedules, support surfaces, skin care, and nutrition. Staging is part of an overall plan that begins with prevention and continues through wound closure.
Stage 1 and Stage 2 — partial-thickness
A Stage 1 pressure injury is intact skin with localized non-blanchable erythema. Pressed, the redness does not turn white. The skin may feel warm, firm, or boggy compared with surrounding tissue. Stage 2 is partial-thickness skin loss involving the epidermis and possibly dermis: it appears as a shallow open ulcer with a red-pink wound bed, or as an intact or ruptured serum-filled blister. Both stages typically respond to prompt pressure redistribution (turning every 2 hours, pressure-relieving mattress or cushion, heel offloading), gentle skin care, and protective dressings. Most early-stage injuries can heal within days to a few weeks if pressure is removed.
Stage 3 and Stage 4 — full-thickness
A Stage 3 injury is full-thickness skin loss; subcutaneous fat may be visible but bone, tendon, and muscle are not exposed. Slough may be present without obscuring the depth. A Stage 4 injury exposes muscle, tendon, ligament, cartilage, or bone, often with undermining and tunneling. Full-thickness injuries require structured wound care: debridement of necrotic tissue, advanced dressings matched to drainage, often negative pressure wound therapy (NPWT), nutritional support (adequate protein and calories), and offloading. Healing is measured in weeks to months. Stage 4 wounds over bone raise concern for osteomyelitis and may need imaging and surgical evaluation.
Unstageable injuries — depth obscured
An Unstageable pressure injury is full-thickness skin and tissue loss in which the actual depth cannot be determined because the wound base is covered by slough (yellow, tan, gray, green, or brown) or eschar (tan, brown, or black). Once enough non-viable tissue is removed to expose the wound base, the injury can be re-staged as Stage 3 or Stage 4. NPIAP guidance: stable, dry eschar on an ischemic limb (especially heel) should generally not be removed because it acts as a biologic cover; unstable eschar (drainage, fluctuance, surrounding redness) needs debridement. This is a clinician judgment, not a home decision.
Deep Tissue Pressure Injury (DTPI)
DTPI presents as intact or non-intact skin with a localized area of persistent non-blanchable deep red, maroon, or purple discoloration, or a blood-filled blister, caused by damage to underlying soft tissue from intense or prolonged pressure or shear. The injury may evolve rapidly to reveal the actual extent of underlying damage, sometimes converting to a Stage 3 or Stage 4 wound within days. DTPI is dangerous because the visible surface understates the deeper injury. NPIAP recommends close monitoring, aggressive offloading, and avoiding massage of the area, which can worsen tissue damage.
When to See a Wound Care Specialist
See a wound care specialist for any pressure injury that has not improved within one to two weeks of consistent offloading, any full-thickness wound, any wound with exposed bone or tendon, or any rapidly worsening discoloration that may be a deep tissue pressure injury. Spreading redness, foul drainage, fever, or sudden increase in pain warrant same-day medical attention — these may indicate infection. Caregivers of bed-bound or chair-bound patients should not wait for a wound to deepen; early specialist involvement and prevention strategies substantially reduce the risk of progression to Stage 3 or 4.
People Also Ask
Common Questions
What is the difference between a pressure ulcer and a pressure injury?
They are the same condition with updated terminology. NPIAP changed the term from "pressure ulcer" to "pressure injury" in 2016 because Stage 1 and Deep Tissue Pressure Injury involve intact skin, where "ulcer" (an open wound) was inaccurate. Many clinicians and patients still use "pressure ulcer" interchangeably; both refer to localized skin and underlying tissue damage caused by pressure, often combined with shear, over a bony prominence.
Can a Stage 1 pressure injury heal on its own?
Often yes, if pressure is removed promptly. Stage 1 is non-blanchable redness on intact skin. Repositioning at least every two hours, using a pressure-redistributing mattress or cushion, keeping skin clean and moisturized, and protecting the area can resolve a Stage 1 injury within days. If the redness does not improve within 24–72 hours of consistent offloading, or if the skin breaks open, the injury is progressing and needs clinical evaluation.
Why is an Unstageable pressure injury unstageable?
Because the wound base is covered by slough or eschar, the clinician cannot see how deep the tissue damage goes. Once enough of that non-viable tissue is removed (debrided) to expose the wound base, the injury is reclassified as Stage 3 or Stage 4 depending on what is visible. Stable dry eschar on certain locations (notably the heel) is sometimes left intact when removing it would expose deeper ischemic tissue.
How long does it take a Stage 3 or Stage 4 pressure injury to heal?
Full-thickness pressure injuries typically heal over weeks to many months, depending on size, depth, location, infection, blood flow, nutrition, and how consistently pressure is offloaded. Some Stage 4 injuries do not close fully without surgical reconstruction (flap closure). Healing is faster when nutrition is optimized (adequate protein and calories), pressure is reliably redistributed, and underlying conditions (diabetes, vascular disease) are well controlled.
Can pressure injuries be prevented?
Most pressure injuries are preventable. AHRQ's prevention toolkit emphasizes structured risk assessment (Braden Scale), repositioning schedules, pressure-redistributing support surfaces, daily skin inspection, moisture management, and adequate nutrition. Family caregivers of bed- or chair-bound patients should learn safe repositioning, heel offloading techniques, and how to inspect the skin daily. Early recognition of a Stage 1 injury and prompt offloading prevents progression to deeper, harder-to-heal stages.
Related Services
References
- NPIAP Pressure Injury Stages — National Pressure Injury Advisory Panel
- Preventing Pressure Ulcers in Hospitals — Toolkit — Agency for Healthcare Research and Quality (AHRQ)
- Pressure Sores — Patient Reference — NIH MedlinePlus
- Prevention and Treatment of Pressure Ulcers/Injuries: Clinical Practice Guideline — NPIAP / EPUAP / PPPIA International Guideline
General information, not medical advice. This page is educational. It does not create a physician-patient relationship and is not a substitute for evaluation, diagnosis, or treatment by a qualified clinician familiar with your individual history. If you have a wound that is worsening, severely painful, rapidly spreading, or accompanied by fever, seek in-person care or call 911. Please do not send protected health information (photos, medical records, diagnoses) through unencrypted email or web forms; call the clinic directly to discuss your situation.
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