A decubitus ulcer is a wound that forms when sustained pressure on the skin cuts off blood flow to the tissue underneath, causing it to break down and die. You may also hear these called bedsores, pressure ulcers, or pressure injuries. They most commonly develop over bony areas like the tailbone, heels, hips, and ankles in people who are bedridden or use a wheelchair for extended periods. Since 2016, the preferred clinical term has been “pressure injury,” a change made by the National Pressure Injury Advisory Panel to reflect that tissue damage begins before the skin visibly breaks open.
How Pressure Injuries Form
Your smallest blood vessels, capillaries, deliver oxygen and nutrients to every layer of skin and the tissue beneath it. When a bony prominence like the sacrum or heel presses against a surface for too long, that pressure squeezes capillaries shut. The tissue downstream is starved of oxygen, a state called ischemia. If the pressure is relieved and blood rushes back in, the sudden return of oxygen can trigger a second wave of damage through what researchers call reperfusion injury. Animal studies have shown that tissue destruction increases with both the duration of each pressure episode and the number of times blood flow is cut off and restored.
Shear force compounds the problem. When the head of a hospital bed is raised, for instance, the body slides slightly while the skin over the tailbone stays anchored. This pulls and distorts blood vessels in deeper layers of tissue, accelerating damage even when surface pressure alone might not be enough to cause a wound.
Where They Develop Most Often
Pressure injuries form over bony prominences where there is little fat or muscle to cushion the tissue. For someone lying on their back, the sacrum (the flat bone at the base of the spine) and the heels are the two most common sites. Side-lying positions put the hips and ankles at risk. People who sit for long stretches in wheelchairs are more vulnerable at the sitting bones (ischial tuberosities) and the tailbone. Less obvious locations include the back of the head, the ears, and the bridge of the nose, particularly for patients wearing medical devices like oxygen masks or tubing.
Stages of a Pressure Injury
Pressure injuries are classified into stages based on how deep the damage extends.
- Stage 1: The skin is still intact, but a localized area (usually over a bony prominence) is persistently red and does not turn white when you press on it. The spot may feel warmer, cooler, firmer, or softer than surrounding skin. In people with darker skin tones, this redness can be difficult to see, making Stage 1 injuries easy to miss.
- Stage 2: The top layers of skin have broken. The wound looks like a shallow open sore, a blister, or an abrasion. The wound bed is typically pink or red and free of dead tissue.
- Stage 3: The full thickness of skin is lost. The wound extends into the fat layer beneath the skin but has not yet reached muscle or bone. It often appears as a deep crater and may have tunneling or undermining at the edges. How deep a Stage 3 wound looks depends on location: over the nose or ear, where there is almost no subcutaneous fat, it can be shallow; over the buttocks, it can be very deep.
- Stage 4: The wound extends through all layers of skin and fat and exposes or directly damages muscle, tendon, or bone. These are the most severe open wounds and carry the highest risk of life-threatening infection.
- Unstageable: The wound bed is covered by dead tissue (slough or a thick black scab called eschar) that prevents a clear view of how deep the injury goes. Until that dead tissue is removed, the true stage cannot be determined.
- Deep tissue injury: The skin is intact, but a deep bruise-like discoloration (purple or maroon) or a blood-filled blister signals that tissue beneath the surface has already been destroyed. These injuries can rapidly worsen and evolve into Stage 3 or 4 wounds even with aggressive care.
Who Is Most at Risk
Healthcare providers assess risk using the Braden Scale, which scores six factors: sensory perception (the ability to feel discomfort from pressure), physical activity level, mobility, moisture exposure, nutritional status, and friction or shear. Scores range from 6 to 23, with lower numbers indicating higher risk. A score of 15 to 18 signals mild risk, 13 to 14 moderate risk, 10 to 12 high risk, and 9 or below severe risk.
In practical terms, the people at greatest risk include those who cannot reposition themselves, such as patients with spinal cord injuries, stroke, or heavy sedation. Elderly patients are especially vulnerable. Roughly 15% of older adults admitted to a hospital develop a pressure injury within the first week. Incontinence keeps skin constantly moist and weakens its outer barrier. Poor nutrition, particularly low protein intake, slows tissue repair and makes skin more fragile in the first place. Diabetes and vascular disease reduce blood flow to the skin, lowering the threshold of pressure needed to cause damage.
Complications of Advanced Wounds
When a pressure injury deepens to Stage 3 or 4, the open wound becomes a gateway for bacteria. One of the most serious complications is osteomyelitis, an infection of the underlying bone. A retrospective study of patients with late-stage pressure sores found that 59% had histologically confirmed bone infection across their treatment course. At the first surgical procedure, 39% of bone samples tested positive; by the third procedure, that number climbed to 70%. Patients with persistent bone infection stayed in the hospital significantly longer, a median of 44 days compared to 28 days for those without it.
Sepsis, a body-wide inflammatory response to infection that can lead to organ failure, is the most dangerous complication. In patients with advanced pressure injuries, the primary reason for antibiotic treatment is typically to manage active sepsis rather than to treat bone infection alone, especially given the growing concern over antibiotic-resistant bacteria.
How Pressure Injuries Are Treated
Treatment depends on the stage of the wound. Stage 1 and 2 injuries are managed by relieving pressure, keeping the wound clean, and maintaining a moist healing environment with appropriate dressings. The goal is to protect the remaining skin and allow the body’s own repair mechanisms to work.
For deeper wounds, removing dead tissue is a critical step. This process, called debridement, can happen in several ways. The gentlest approach uses moisture-retaining dressings that let the body’s own enzymes dissolve dead tissue gradually, a technique suited for wounds that are not infected. Enzyme-based treatments apply a protein-dissolving agent directly to the wound to break down dead tissue more quickly. When infection is present or the wound contains thick, hard dead tissue, a surgeon removes it with a scalpel or other instruments. Surgical debridement also allows for accurate cultures of the remaining tissue, which helps guide antibiotic choices if infection is confirmed.
Stage 4 wounds that do not respond to conservative care may require reconstructive surgery, in which a flap of healthy tissue is moved to cover the wound and provide a cushion over the exposed bone.
The Role of Nutrition in Healing
Wound healing is an energy-intensive process, and protein is the primary building material for new tissue. Guidelines recommend that people with pressure injuries consume 30 to 35 calories per kilogram of body weight per day and significantly more protein than the general population. For Stage 1 and 2 wounds, the target is 1.0 to 1.4 grams of protein per kilogram of body weight daily. For Stage 3 and 4 wounds, that target rises to 1.5 to 2.0 grams per kilogram, with a maximum of 2.2 grams per kilogram for the largest or most draining wounds.
To put that in perspective, a 150-pound person (68 kg) with a Stage 3 wound would need roughly 100 to 136 grams of protein per day. That is roughly double what most adults eat. Vitamins A, C, and E, along with zinc, also support wound repair, though the ideal amounts are not precisely established. For patients who struggle to eat enough, oral nutritional supplements or fortified foods are commonly used to close the gap.
Preventing Pressure Injuries
Repositioning is the single most important preventive measure. People assessed as being at risk should change position at least every six hours. Those at high risk should reposition at least every four hours. In practice, many care settings aim for every two hours, though evidence suggests that less frequent turning combined with a pressure-redistributing mattress can be equally effective. One study of nearly 600 patients found that four-hourly repositioning on a specialized mattress prevented more pressure injuries than standard care.
Pressure-redistributing surfaces, including foam mattresses, alternating-pressure air mattresses, and wheelchair cushions, spread body weight over a larger area so no single point bears too much force. Keeping skin clean and dry, managing incontinence promptly, and ensuring adequate nutrition round out a prevention plan. For anyone caring for a loved one at home, the priorities are straightforward: help them move often, check their skin daily (especially the tailbone and heels), keep their skin moisturized but not wet, and make sure they are eating enough protein.