An ulcer is any open sore or wound. Most people first think of a stomach condition when they hear the term "ulcer," but it is also commonly a disorder of the skin. People with diabetes are at higher risk of skin ulcers, especially on the feet and legs.

Foot ulcers may be caused by injury or improper foot care. People with diabetes face increased risk of foot trauma because of numbness due to nerve damage (diabetic neuropathy) and impaired circulation. Foot ulcers are so common and serious with diabetes that they are often used as a synonym for diabetic ulcers.

People with diabetes account for 7 percent of the population yet undergo more than 60 percent of foot or leg amputations in the United States, according to the Centers for Disease Control and Prevention (CDC). Of those diabetic amputations, 85 percent are preceded by a foot ulcer. The CDC also reports that among American adults with diabetes, about 12 percent have had a foot ulcer. Diabetic foot ulcers are most common among individuals who:

• Smoke
• Are obese
• Use insulin
• Have had diabetes for two decades or more
• Are white or Hispanic
• Are male

A pressure ulcer is damage to the skin, and in more serious cases the underlying tissue, caused by impaired circulation due to pressure on a specific area. The skin begins to die when the supply of blood is stopped for more than a couple of hours. Pressure ulcers most commonly occur in individuals who spend most of their time in a bed or chair without repositioning. Pressure ulcers also may occur from straps, splints, a cast or ill-fitting clothes.

Diabetes is one of several chronic diseases that elevate the risk of pressure ulcers because of neuropathy, impaired circulation and the increased possibility of impaired mobility. Poorly controlled glucose (blood sugar) also contributes to the development of pressure ulcers. People who are confined to a bed or a wheelchair because of severe diabetes or other debilitating conditions are at highest risk.

Parts of the body most likely to develop pressure ulcers are bony areas beneath the skin and areas in contact with a bed or chair. These body parts include elbows, shoulders, back, buttocks, hips, ankles, heels and the back of the head.

Pressure ulcers often heal on their own when caught early and the source of pressure is resolved. However, serious cases can lead to infection of the underlying muscle and even of the bone (osteomyelitis). These infections can lead to gangrene (tissue death) that may require amputation of a limb.

Diabetic conditions, such as high blood glucose (hyperglycemia), impaired circulation and nerve damage, increase the risk of infection and impede the healing of wounds. Thus the presence of slow-healing skin ulcers may be a sign of diabetes that has not yet been diagnosed.