What Is Pressure Injury: What Stage Is Pressure Injury of the Skin? A Stage-by-Stage Guide

What Is Pressure Injury: The Six Stages That Classify Skin and Tissue Damage

A pressure injury is localized damage to skin and underlying tissue caused by sustained pressure, or pressure combined with shear and friction, usually over a bony prominence. The stage tells you how deep that damage runs: Stage 1 is intact skin with non-blanchable redness, Stage 2 is partial-thickness skin loss, Stage 3 is full-thickness loss reaching fat, Stage 4 exposes fascia, muscle, tendon, or bone, and two unstageable categories cover wounds hidden by slough or eschar or by deep tissue injury. When someone asks "what stage is pressure injury of the skin," the honest answer is that staging is a classification of depth assigned by a trained clinician at the bedside, and it dictates the dressing, support surface, and repositioning plan that follows.

The term replaced "pressure ulcer" and "bed sore" in the 2016 revision of the National Pressure Injury Advisory Panel's staging system, now in its fourth edition. That matters for anyone reading older charts or discharge summaries, because a 2014 record that says "decubitus ulcer stage II" describes the same thing a 2026 record calls a Stage 2 pressure injury. The naming changed to reflect that these wounds begin in tissue before skin ever breaks.

Why a Pressure Injury Is Tissue Damage Before It Is a Skin Wound

The mechanism explains the staging. Pressure above the capillary closing pressure — commonly cited around 32 mmHg in the literature on capillary perfusion — collapses small blood vessels and starves tissue of oxygen. Muscle and subcutaneous fat are softer and more pressure-sensitive than skin, so in many cases the deepest damage sits beneath an intact surface. This is exactly why a Stage 1 wound can look like a minor red patch and still be the visible tip of an injury that began in deeper layers.

Three forces work together. Pressure compresses tissue between a bony prominence and a hard surface. Shear happens when the skeleton slides inside the skin, as when a head of a bed is raised and the patient slides down, which stretches and tears internal tissue planes. Friction abrades the surface and matters most for people who cannot reposition themselves. The classic high-risk locations reflect anatomy: the sacrum and coccyx, heels, ischial tuberosities, greater trochanters, occiput, and, in people who use medical devices, the skin under a mask, oxygen tubing, or a cervical collar.

Bony prominence locations concentrate force. A sacral wound sits over the point where the sacrum contacts the mattress, and a heel wound involves a small surface area carrying a disproportionate amount of body weight. The National Pressure Injury Advisory Panel staging system, published in its fourth edition in 2016, formalized the depth categories that ran through clinical practice since the 1980s. Understanding the mechanism tells you why a red mark on the heel is not cosmetic and why "keep it off the pressure" is a treatment instruction, not comfort advice.

Common conditions that raise risk include immobility, reduced sensation, malnutrition, moisture from incontinence, advanced age, and critical illness with vasopressor support. The Braden Scale, a six-item risk assessment scoring sensory perception, moisture, activity, mobility, nutrition, and friction/shear on a scale where lower scores mean higher risk, is the most widely used screening tool in United States hospitals. A score of 18 or below is generally treated as at risk in acute care, with the precise cutoff varying by care setting. Risk score does not determine stage — depth does.

The Six Pressure Injury Stages, Compared Side by Side

Staging is determined by the deepest tissue layer visible or palpable, and the two unstageable categories exist precisely because depth cannot be confirmed until something changes. The table below compresses what a clinician documents for each category and what typically appears in the wound bed.

Stage 1 has no dressing because there is no break in the skin; management is offloading, moisture management, and documentation with a photograph and description. Stage 2 wounds, by contrast, need a dressing that maintains a moist environment and protects fragile periwound skin — hydrocolloid or foam are common choices, and clinicians confirm specific product selection with the wound care team. Stage 3 and 4 wounds involve significant tissue loss and often undermining, meaning the wound extends sideways under intact skin edges.

Timing numbers vary by source and patient. The widely taught "turn every 2 hours" originates in Florence Nightingale-era nursing practice and is not derived from a randomized trial; modern guidance from the National Pressure Injury Advisory Panel favors individualized turning schedules based on the support surface and tissue tolerance, with high-density foam or specialty surfaces often extending intervals to 4 hours. If a Stage 1 area does not improve within 24 to 48 hours of consistent offloading, the correct response is reassessment, not waiting longer.

A common failure case: a sacral wound with a black eschar on admission gets documented as "Stage 4" by a rushed clinician. It cannot be staged until the eschar is debrided or naturally separates, so the correct label is "unstageable — eschar." If that same patient's eschar is on a heel and there is no palpable pulse, debridement may be contraindicated. Document the unstageable category and involve vascular and wound specialists.

Stage 1 Versus Stage 2: The Boundary That Changes Liability

Blanchability is the test that separates a pressure injury from a bruise or reactive hyperemia. Press a fingertip or a transparent disc on the reddened area and release; if the redness fades, it is blanchable and likely reactive, not a Stage 1 injury. If the color persists — especially in people with darker skin tones where the change appears as a purplish or bluish hue — it counts as a Stage 1 pressure injury. Skin tone can make Stage 1 harder to detect, which is why clinicians palpate for warmth, firmness, or boggy texture alongside color change rather than relying on visual redness alone.

Stage 2 is the earliest open wound and the most commonly miscoded stage. It presents as a shallow, partial-thickness wound with a pink or red bed without slough, or as a blister. Incontinence-associated dermatitis — a moisture-driven skin irritation in the same pelvic region — is the classic imitation, and the two get confused constantly. A Stage 2 wound has definable wound edges; dermatitis spreads in patches with irregular margins and no depth.

A 2019 study published in BMJ Open tracking pressure injury incidence in United States acute care hospitals found that Stage 2 injuries were the most frequently recorded stage in many facility datasets. That matters because Stage 2 is often the stage where documentation accuracy is tested in survey and litigation contexts. A common failure scenario: a clinician labels a moisture lesion from urinary incontinence as a Stage 2 injury. That inflates reported pressure injury rates and triggers the wrong intervention — moisture management rather than pressure offloading — while the true injury risk goes unaddressed.

The practical consequence is a rule nursing homes and hospitals use. Before documenting any Stage 2 wound, confirm the wound has a defined margin rather than diffuse redness, and rule out moisture, friction, or a skin tear from tape. If the distinction is unclear, consult wound care and photograph the area. Mistakes in this boundary are more than academic — they change outcome reporting and, in some states, appear in public quality databases.

Stage 3 and Stage 4: When Deeper Layers and Infection Take Over

Stage 3 pressure injuries involve full-thickness skin loss reaching subcutaneous fat. Granulation tissue — the beefy red tissue that fills a healing wound — often sits alongside slough, the yellow or tan material that needs removal. Undermining and tunneling are hallmarks: the wound edges lift away from the base, forming a cavity under intact skin. These injuries need a moist wound-healing environment with packing for dead space, and they routinely require a wound care nurse or specialist, not standard floor dressing protocols.

Stage 4 injuries expose fascia, muscle, tendon, cartilage, or bone. The risk at this depth is osteomyelitis, infection of the underlying bone, and the wound team manages it jointly with imaging and, in many cases, surgery. Stage 4 pressure injuries are relatively rare but account for a disproportionate share of serious complications and length-of-stay costs. A commonly cited figure from the Agency for Healthcare Research and Quality attributed approximately $9.1 billion to $11.2 billion in United States acute care costs to hospital-acquired pressure injuries per year across all stages, with Stage 4 wounds among the most expensive per case.

A case that clinicians should recognize: a Stage 4 sacral wound appears "clean" but the patient has unexplained fever and rising inflammatory markers. Imaging and a bone biopsy evaluation — not just wound inspection — are the correct path, because exposed bone under a sacral wound is the scenario in which osteomyelitis develops without obvious surface change. Coordination between wound care, orthopedic surgery, and infectious disease is standard at that depth.

Depth determines surgery. Stage 4 wounds with necrotic tissue may need sharp debridement by qualified clinicians, and some require flap reconstruction. Stage 3 wounds with tunneling need packing, not just a dressing. A cardinal failure case is aggressive debridement of a heel eschar in a patient with peripheral arterial disease, which can turn a stable eschar into a non-healing ulcer or gangrene. Vascular assessment — palpable pulses, ankle-brachial index where indicated — precedes debridement decisions on the feet.

Omitted Stages 5 and 6, and Why Older Charts Say "Decubitus Ulcer"

Two stage numbers do not exist in the modern system. Vietnam-era practice had a Stage V and Stage VI reference in some military medical records, and older United States charts sometimes used a six-level scheme. The current National Pressure Injury Advisory Panel system stops at Stage 4 and adds two unstageable categories. If a scan or archive search turns up a "Stage 5 pressure ulcer," the correct response is to treat it as historical terminology, interpret the depth from the wound description, and not carry the number forward.

The vocabulary changed too. The same injuries were called decubitus ulcers, bed sores, and pressure sores for decades. In 2016, the National Pressure Injury Advisory Panel adopted "pressure injury" to acknowledge that these wounds can begin beneath intact skin, which the word "ulcer" never captured. That language shift appears in regulatory guidance, quality-reporting definitions, and clinical documentation templates. If a family member is reading a 2008 discharge summary that says "stage III decubitus ulcer of the sacrum," the modern equivalent is a Stage 3 pressure injury at the sacrum — same wound, recognized differently.

Staging systems also differ across contexts. The National Pressure Injury Advisory Panel system is used across most United States and international wound care settings. In some long-term care and reimbursement contexts, the Minimum Data Set field definitions in the United States add details about wound status that are not stages in the clinical sense — they are documentation fields for payment and quality reporting, not depth categories. Confusion between clinical stage and billing data fields is a real operational problem in nursing homes.

Practical misuse to recognize: describing a wound as "stage 2–3" as if it straddles categories. The staging system is categorical and hierarchical, and a wound is assigned one stage based on the deepest visible layer. There is no "stage 2.5." A wound that appears to straddle is usually one where debridement or a specialist reassessment is overdue. Staging should be documented once per assessment, with date, time, location, measurements, and the basis for the stage.

What Staging Determines for the Care Team

Stage drives the treatment plan, not the other way around. Stage 1 gets offloading and prevention, Stage 2 gets a protective dressing and moist wound care, Stage 3 and 4 get complex wound management, and unstageable categories get a debridement or monitoring plan. A Stage 1 sacral injury on a patient with limited mobility moves them to a pressure-redistribution mattress and structured repositioning. A Stage 3 sacral injury may move them to a specialty surface and involve a wound care consult within 24 hours — the timeline varies by facility policy, and the care team's plan should be followed.

Support surfaces are stage-specific engineering. Alternating pressure air mattresses redistribute load mechanically and are used for high-risk and Stage 3–4 wounds, while static high-density foam mattresses suit lower-risk patients and often permit longer turning intervals. Heel offloading boots suspend the heel entirely and are standard for heel pressure injuries. Repositioning intervals of 30 degrees lateral tilt — as opposed to full side-lying — are commonly used to reduce pressure on trochanters.

Nutrition is part of the stage plan, not an optional add-on. Wound healing requires protein and calories, and nutrition screening should happen with the wound assessment. Malnutrition is one of the strongest modifiable risk factors, and registered dietitians routinely review Stage 3 and 4 cases. Pressure injuries also drive reimbursement and public reporting in many countries — quality metric reporting requirements include hospital-acquired pressure injuries as adverse events under the Agency for Healthcare Research and Quality's definitions — which is why accurate staging is documented with evidentiary rigor.

A high-frequency edge case is device-related pressure injury. A patient's bilevel positive airway pressure mask, oxygen nasal cannula, cervical collar, or cast can create a localized injury that is technically a pressure injury but not staged from a bony prominence. The National Pressure Injury Advisory Panel's fourth edition explicitly recognizes medical device-related pressure injuries as a separate causation category. These injuries are often missed, and a mask strap that leaves a persistent mark on the bridge of the nose is worth documenting and offloading.

Staging Is a Bedside Judgment, Not a Diagnosis You Can Make Alone

Scope and limit are essential here. Stage classification, wound assessment, debridement decisions, and dressing selection belong to a trained clinician — typically a registered nurse with wound expertise, a wound care certified nurse, a physician, or a podiatrist. The National Pressure Injury Advisory Panel staging system is the reference framework, and its fourth edition (2016) is the current published standard. Anyone using this article to identify their own wound should treat it as a prompt to seek assessment, not as a substitute.

If you're a caregiver or patient watching an area of redness or a shallow wound, the practical instruction is to photograph it, note the date, keep pressure off it, and get it assessed. Photographs taken with consistent lighting and a ruler are often the difference between early detection and progression. A person with limited mobility cannot perform effective repositioning alone, and the turning schedule is part of a team plan.

Immediate danger signs that warrant urgent evaluation include rapidly spreading redness, foul odor, fever, new pain at the site, or exposed bone. These suggest infection or deep involvement and need same-day clinical review, not at-home dressing changes. For someone with diabetes or peripheral artery disease, any new foot wound is urgent — the risk of complications runs higher in that population.

This article is general educational information about the pressure injury staging system and is not a diagnosis, treatment plan, or substitute for clinical assessment. Pressure injury staging, wound care, and debridement decisions require a locally qualified clinician, and care standards differ by country, facility, and clinical setting. If a wound is worsening or you're concerned about infection, contact a qualified healthcare professional promptly; for immediate danger, call local emergency services.

FAQ

What percentage of pressure injuries are Stage 1?

Facility-reported distributions vary widely, but Stage 1 injuries are usually the most common stage recorded in acute care point-prevalence surveys, often accounting for roughly 40 to 50 percent of identified pressure injuries when surveys include non-blanchable erythema. The exact proportion depends on assessment technique and whether surveys use blanching tests consistently with darker skin tones. That is why survey methodology is published alongside the figures rather than as a single national statistic.

Can a Stage 1 pressure injury become a Stage 4 in the same admission?

Yes, progression is possible, and it is the reason early offloading matters. A Stage 1 area that stays under pressure, especially over a sacrum or heel in an immobile patient, can progress through all stages in days to weeks. Onset is often faster in critical care patients with poor perfusion. Monitoring intervals and turning schedules are designed to catch this early, not to wait for progression.

Is a pressure injury the same as a bedsore?

They describe the same injury family, with different vocabulary eras. Bedsores, pressure ulcers, and decubitus ulcers are older names for what the National Pressure Injury Advisory Panel now calls pressure injuries. The modern term intentionally includes injuries that begin beneath intact skin. Charts from before 2016 will likely use the older terminology, and the staging numbers usually map directly onto today's system.

How much does treating a hospital-acquired pressure injury cost per case?

The Agency for Healthcare Research and Quality cites total United States acute care annual costs of $9.1 billion to $11.2 billion for hospital-acquired pressure injuries, with per-case costs rising substantially with stage. Figures for individual cases vary by facility, wound depth, and complications like infection or surgery. Those cost figures are not published as a single per-patient price — they are aggregate estimates from the agency's analyses.

Why would a wound be called "unstageable" instead of Stage 4?

Because the wound base is hidden. Slough or eschar covers the deepest layer, and staging requires seeing or palpating the actual depth. An unstageable wound is not necessarily severe — it is unknown severity. The correct next step is debridement or monitoring until the base is visible, then assignment of the appropriate stage. A common error is calling a covered wound Stage 4 by assumption.

Are pressure injuries always on bony areas?

No, and this is where medical device injuries get missed. Nasal bridge marks from a mask or cannula, ear injuries from oxygen tubing, and occipital and heel injuries from positioning are common non-bony presentations. The National Pressure Injury Advisory Panel treats medical device-related pressure injuries as a distinct causation category. If you see a persistent mark under a device, it should be assessed and documented.

Does a Stage 2 injury heal on its own without intervention?

Not reliably, and not without offloading. A Stage 2 wound may close in days to weeks with appropriate offloading, moist wound care, and nutrition, but continuing pressure on the site can turn it into a deeper wound. If a Stage 2 area is not showing improvement in one to two weeks, reassessment is warranted. People with diabetes, poor circulation, or malnutrition heal more slowly and need earlier specialist input.