Pressure Injury Staging: Stages 1 to 4, Unstageable, and Deep Tissue

Staging a pressure injury comes down to one question: how deep does the damage go? Stage 1 is intact skin with redness that will not blanch, Stage 2 breaks into the dermis, Stage 3 exposes the fatty layer underneath, and Stage 4 reaches muscle, tendon, or bone. When slough or eschar hides the base so you cannot judge the depth, the wound is unstageable, and when the skin sits over a deep purple bruise or a blood-filled blister, it is a deep tissue pressure injury. Learn the signature look and the first nursing action for each, and these questions become quick points.

Staging is a depth question, not a timeline

The single idea that unlocks this whole topic is that the stage names a depth of tissue loss, not how old or how bad the wound is. Each step down the list means the injury has reached a deeper layer of tissue: skin, then dermis, then fat, then muscle and bone. Picture the layers from the surface down and the stages line up with them.

Staging is also not a linear timeline. A pressure injury does not have to start at Stage 1 and climb; a deep tissue injury can appear as intact purple skin and open straight into a full-thickness wound. And you never reverse-stage a healing wound: a healing Stage 4 is documented as a healing Stage 4, it does not become a Stage 3, then 2, then 1 as it fills in. The exam loves both of those traps.

The staging system at a glance

Here is the whole system on one page: what each stage looks like at the bedside and where your nursing focus goes first. Read down the first column, and notice that the look of the wound is what tells you the stage.

Stage 1: intact skin, redness that will not blanch

A Stage 1 injury is a warning shot. The skin is still intact and unbroken, but there is localized non-blanchable redness, usually over a bony prominence like the sacrum, heel, or elbow. The area may feel warmer or cooler, firmer or softer, or more tender than the skin around it. On darker skin tones the color change can be subtle, so temperature, firmness, and tenderness matter even more. Because the skin is unbroken, this is the stage where good nursing can stop the whole process.

Stage 2: into the dermis

A Stage 2 injury is partial-thickness: the top layer of skin is gone and the dermis is exposed. It shows up as a shallow, moist, pink or red open wound, or as an intact or ruptured blister filled with clear, straw-colored serum. The wound is shallow and there is no fat visible, no slough, and no dead tissue. If you can see yellow fat, it is not a Stage 2 anymore. Care aims to keep the wound bed moist and protected so the dermis can heal.

Stage 3: the fatty layer is showing

A Stage 3 injury is full-thickness: the wound now goes all the way through the skin and you can see subcutaneous fat at the base. It often looks like a crater and may have rolled wound edges and undermining (a lip where the wound is wider under the skin than it looks on the surface). What you do not see is muscle, tendon, or bone. Depth varies by body location, since areas like the bridge of the nose have little fat and areas like the buttock have a lot.

Stage 4: muscle, tendon, or bone

A Stage 4 injury is the deepest: full-thickness loss with muscle, tendon, ligament, cartilage, or bone exposed or directly palpable in the wound. Slough or eschar may be present along the edges, and undermining and tunneling are common. Because bone can be involved, osteomyelitis (bone infection) is a real risk, and these wounds need the wound-care team. Recognizing an exposed deeper structure is the whole clue: if you can see or touch bone or tendon, it is a Stage 4.

Unstageable: you cannot see the bottom

A wound is unstageable when it is full-thickness but the base is covered by slough or eschar, so you cannot confirm how deep it goes. Slough is soft, stringy, yellow or tan dead tissue; eschar is thick, leathery, tan, brown, or black. Because the numbered stages depend on seeing the depth, you cannot assign a number until the dead tissue is removed. Once it is debrided, an unstageable wound is revealed to be a Stage 3 or a Stage 4 underneath.

Deep tissue pressure injury: the deep bruise

A deep tissue pressure injury (DTPI) is damage that starts at the bone-muscle interface and works its way up, so the surface can look almost normal at first. It shows as intact or newly broken skin with a persistent, non-blanchable deep red, maroon, or purple area, or as a blood-filled blister. Pain and a temperature change often show up before the color does. This is the trap the exam builds around blisters: a clear serum-filled blister is a Stage 2, but a blood-filled blister is a deep tissue injury. A DTPI can deteriorate into a full-thickness wound quickly even with good care, so it is offloaded and watched closely.

Stage the wound yourself

Recognition is a skill you build by repetition, so practice the call on the free drill below. Each case describes one wound; decide the stage, then reveal the giveaway feature and the first nursing action. Every reveal is tied to the case in front of you, so the answer always matches what you read.

Prevention is the real exam answer

The exam cares more about stopping pressure injuries than treating them, so prevention answers win. The nurse at the bedside is the one who catches risk early, and a lot of these questions reward the basics done consistently. Tie this to the wider reduction of risk content and to who you assess first when several clients are at risk.

• Reposition on a schedule. Turn a client in bed at least every 2 hours and shift a client in a chair every hour; teach an able client to shift weight about every 15 minutes.
• Screen the risk. Use a validated tool like the Braden Scale, where a lower score means higher risk, to flag who needs a prevention plan.
• Redistribute pressure. Use a pressure-redistribution mattress or cushion, and keep heels off the bed with a pillow under the calves.
• Keep skin clean and dry. Manage moisture from sweat, urine, or drainage with barrier products; wet skin breaks down faster.
• Feed the skin. Adequate protein, calories, and hydration give tissue what it needs to stay intact and to heal.
• Inspect every shift. Look at bony prominences, especially the sacrum and heels, and act on the first sign of non-blanchable redness.

• Stage means depth. Stage 1 is intact skin, Stage 2 reaches the dermis, Stage 3 exposes fat, and Stage 4 exposes muscle, tendon, or bone.
• Non-blanchable defines Stage 1. Redness that stays when you press it, over intact skin, is a Stage 1 injury; relieve pressure and never massage it.
• Hidden base means unstageable. If slough or eschar covers the base, you cannot judge depth, so it is unstageable until debrided, revealing a Stage 3 or 4.
• Blister color splits two stages. A clear serum-filled blister is a Stage 2; a blood-filled blister or a deep purple-maroon area is a deep tissue injury.
• Prevent and never reverse-stage. Reposition, offload, keep skin dry, and screen risk; a healing wound keeps its original stage and is called healing.