Warning signs of pressure ulcers are:

• Unusual changes in skin color or texture
• Swelling
• Pus-like draining
• An area of skin that feels cooler or warmer to the touch than other areas
• Tender areas

Bedsores fall into one of several stages based on their depth, severity and other characteristics. The degree of skin and tissue damage ranges from red, unbroken skin to a deep injury involving muscle and bone.

Common sites of pressure sores

For people who use a wheelchair, pressure sores often occur on skin over the following sites:

• Tailbone or buttocks
• Shoulder blades and spine
• Backs of arms and legs where they rest against the chair

For people who are confined to a bed, common sites include the following:

• Back or sides of the head
• Shoulder blades
• Hip, lower back or tailbone
• Heels, ankles and skin behind the knees

Bedsores are caused by pressure against the skin that limits blood flow to the skin. Other factors related to limited mobility can make the skin vulnerable to damage and contribute to the development of pressure sores.

Three primary contributing factors for bedsores are:

• Pressure. Constant pressure on any part of your body can lessen the blood flow to tissues. Blood flow is essential to delivering oxygen and other nutrients to tissues. Without these essential nutrients, skin and nearby tissues are damaged and might eventually die.

For people with limited mobility, this kind of pressure tends to happen in areas that aren't well-padded with muscle or fat and that lie over a bone, such as the spine, tailbone, shoulder blades, hips, heels and elbows.

• Friction. Friction occurs when the skin rubs against clothing or bedding. It can make fragile skin more vulnerable to injury, especially if the skin is also moist.
• Shear. Shear occurs when two surfaces move in the opposite direction. For example, when a bed is elevated at the head, you can slide down in bed. As the tailbone moves down, the skin over the bone might stay in place — essentially pulling in the opposite direction.

People are at risk of developing pressure sores if they have difficulty moving and are unable to easily change position while seated or in bed. Risk factors include:

• Immobility. This might be due to poor health, spinal cord injury and other causes.
• Lack of sensory perception. Spinal cord injuries, neurological disorders and other conditions can result in a loss of sensation. An inability to feel pain or discomfort can result in not being aware of warning signs and the need to change position.
• Poor nutrition and hydration. People need enough fluids, calories, protein, vitamins and minerals in their daily diet to maintain healthy skin and prevent the breakdown of tissues.
• Medical conditions affecting blood flow. Health problems that can affect blood flow, such as diabetes and vascular disease, increase the risk of tissue damage.

Complications of pressure ulcers, some life-threatening, include:

• Cellulitis. Cellulitis is an infection of the skin and connected soft tissues. It can cause warmth, redness and swelling of the affected area. People with nerve damage often do not feel pain in the area affected by cellulitis.
• Bone and joint infections. An infection from a pressure sore can burrow into joints and bones. Joint infections (septic arthritis) can damage cartilage and tissue. Bone infections (osteomyelitis) can reduce the function of joints and limbs.
• Cancer. Long-term, nonhealing wounds (Marjolin's ulcers) can develop into a type of squamous cell carcinoma
• Sepsis. Rarely, a skin ulcer leads to sepsis.