A pressure wound is an area of damaged skin and tissue caused by sustained pressure, typically over a bony part of the body. These injuries range from a persistent red patch on the skin’s surface to deep wounds that expose muscle or bone. You may also hear them called bedsores, pressure sores, or pressure ulcers, though the official medical term since 2016 is “pressure injury,” because the damage can exist even when the skin isn’t visibly broken.
How Pressure Wounds Form
When part of your body presses against a surface for too long, the weight squeezes the tiny blood vessels in your skin and the tissue underneath. That compression cuts off the flow of oxygen and nutrients while waste products like carbon dioxide build up, creating an acidic environment that eventually kills cells. This process, called localized ischemia, is the most widely recognized explanation for pressure wound development.
But blood flow isn’t the only thing affected. The lymphatic vessels, which act as the body’s cleanup system for fluid and waste, are even easier to compress than blood vessels. When lymph flow stalls, swelling and inflammatory byproducts accumulate in the tissue, accelerating damage. Under enough pressure, cells can also be injured directly: the physical deformation warps their internal structure and makes their outer membranes too permeable to function. In high-pressure situations, this kind of direct cell damage can begin within minutes.
There’s also a less intuitive mechanism at play. When pressure is finally relieved and blood rushes back into the starved tissue, the sudden flood of oxygen triggers a burst of harmful molecules called reactive oxygen species. This “reperfusion injury” causes a wave of inflammation that can worsen the damage already done during the period of compression.
Where Pressure Wounds Typically Develop
Pressure wounds form wherever bone sits close to the skin’s surface and presses outward against a mattress, wheelchair seat, or other firm surface. The sacrum (the flat bone at the base of your spine) is the single most common location, followed by the heels. Other frequent sites include the sit bones (ischial tuberosities), the bony bump on the outer hip (greater trochanter), and the ankle bones (malleoli). In reality, a pressure wound can develop anywhere, including behind the ears from oxygen tubing or on the bridge of the nose from a medical device.
Stages of Pressure Injury
Healthcare providers classify pressure wounds into stages based on how deep the damage goes. Understanding these stages helps you recognize what you’re looking at and how serious it is.
Stage 1
The skin is still intact, but there’s a persistent area of redness over a bony spot that doesn’t fade when you press on it. On darker skin tones, the discoloration may not look red but will differ noticeably from the surrounding area. The spot may feel warmer, firmer, or softer than nearby skin. This stage is fully reversible with prompt pressure relief.
Stage 2
The top layers of skin have broken down, creating a shallow open sore with a pink or red wound bed. It may also appear as a fluid-filled or ruptured blister. There’s no dead tissue visible in the wound at this stage.
Stage 3
The damage extends through the full thickness of the skin. You may see fatty tissue at the base of the wound, but bone, tendon, and muscle are not yet visible. The wound may tunnel under the surrounding skin, making it larger beneath the surface than it appears from the outside.
Stage 4
This is the most severe stage, with full-thickness tissue destruction that exposes bone, tendon, or muscle. Tunneling and undermining of surrounding tissue are common. These wounds carry the highest risk of serious complications.
Unstageable and Deep Tissue Injuries
Sometimes a wound can’t be staged because its base is covered by a layer of dead tissue (slough or eschar) that hides the true depth. These are classified as unstageable until the dead tissue is removed. A deep tissue pressure injury is a distinct category: the skin may still be intact, but a purple or maroon discoloration signals that significant damage has occurred in the layers beneath. The area often feels painful, boggy, or unusually firm compared to the tissue around it.
Who Is Most at Risk
Anyone who can’t shift their body weight regularly is vulnerable. This includes people who are bedridden after surgery, those with spinal cord injuries, older adults with limited mobility, and people who use wheelchairs for extended periods. But immobility alone doesn’t tell the whole story.
Clinicians use a tool called the Braden Scale to evaluate risk. It scores six factors: sensory perception (whether you can feel discomfort that would prompt you to shift position), moisture exposure, physical activity level, mobility, nutritional status, and friction or shear on the skin. Scores range from 6 to 23, and anything at or below 18 signals increased risk. A lower score means higher risk. Poor nutrition, incontinence, reduced sensation (from diabetes or nerve damage, for example), and thin or fragile skin all push the risk higher.
Prevention Through Repositioning and Support
The most effective prevention strategy is regular repositioning. For someone lying in bed, changing position every two to three hours is the standard recommendation, provided they’re also on an appropriate pressure-redistributing mattress. Extending those intervals beyond three hours is generally not advised. For someone sitting in a wheelchair, smaller shifts in weight should happen more frequently.
These intervals aren’t rigid rules. A good repositioning plan considers the whole 24-hour day, including sleep, and accounts for the person’s skin tolerance, overall health, comfort, and the type of support surface they’re using. Someone on a high-quality pressure-relieving mattress may tolerate slightly different timing than someone on a standard hospital bed, but the core principle remains: sustained, unrelieved pressure is the enemy.
Keeping skin clean and dry, inspecting vulnerable areas daily (especially over bony prominences), using pillows or foam wedges to offload pressure between the knees and ankles, and ensuring good nutrition all reduce risk significantly.
Why Nutrition Matters for Healing
Healing a pressure wound demands extra energy and building materials from the body, particularly protein. The general recommendation for someone with a pressure injury is 1.2 to 1.5 grams of protein per kilogram of body weight daily. For a 150-pound person, that translates to roughly 82 to 102 grams of protein per day, significantly more than most people eat by default. Those who are bedridden or severely ill may need up to 2 grams per kilogram. Good sources include eggs, dairy, poultry, fish, beans, and protein supplements when food intake alone falls short.
Adequate hydration, vitamins (particularly vitamin C and zinc), and sufficient overall calorie intake also support wound healing. Malnutrition is both a risk factor for developing pressure wounds and a barrier to healing existing ones, making nutritional assessment a key part of any treatment plan.
How Pressure Wounds Are Treated
Treatment depends on the wound’s stage and characteristics. For stage 1 injuries, relieving pressure and protecting the skin is often enough. For open wounds, the goal is to maintain a moist healing environment, which speeds tissue repair and reduces pain during dressing changes.
The type of dressing used depends on how much fluid the wound produces. Wounds that drain moderately to heavily benefit from foam, alginate, or hydrocolloid dressings. Alginate dressings, derived from seaweed, form a gel when they contact wound fluid and can stay in place for several days. They’re rinsed away with saline rather than peeled off, which makes changes less painful. Foam dressings absorb well and can be used to fill wound cavities, though they typically need daily replacement. Hydrocolloid dressings retain moisture and also help the body naturally break down dead tissue through a process called autolytic debridement, though some people develop skin irritation from them.
Dry wounds call for hydrogel dressings, which are more than 95% water and can donate moisture to a wound that needs it. In all cases, dead tissue in the wound bed needs to be removed (debrided) to allow healthy tissue to grow. This can happen through specialized dressings, enzyme-based treatments, or procedures performed by a wound care specialist.
Potential Complications
Left untreated or poorly managed, pressure wounds can lead to serious health problems. Cellulitis, a spreading bacterial infection of the skin and underlying tissue, is one of the most common complications. When a stage 4 wound exposes bone, the infection can reach the bone itself, causing osteomyelitis. Bone infections can reduce joint function and are difficult to treat, sometimes requiring weeks of targeted treatment.
In rare cases, bacteria from an infected pressure wound enter the bloodstream and trigger sepsis, a life-threatening whole-body inflammatory response. There’s also a long-term risk: chronic, nonhealing pressure wounds that persist for years can undergo cancerous changes, developing into a type of skin cancer known as a Marjolin ulcer. These complications underscore why early detection and consistent management matter so much, even for wounds that initially appear minor.