Chronic wounds (ulcers) do not heal or heal slowly because an underlying defect (e.g. diabetes mellitus, or continued pressure) that impedes local blood flow and arrests progress through the phases of wound healing.

Chronic wounds may never heal or may take years to do so. These wounds cause patients severe emotional and physical stress and create a significant financial burden on patients and the whole healthcare system

In addition to poor circulation, neuropathy, and difficulty moving, factors that contribute to chronic wounds include systemic illnesses, age, and repeated trauma.

The main three types of chronic wounds include: diabetic ulcers, venous ulcers and pressure ulcers

1.      Diabetic ulcers
A major cause of chronic wounds, diabetes, is increasing in prevalence. Diabetics have a 15% higher risk for amputation than the general population due to chronic ulcers. Diabetes causes neuropathy, which inhibits nociception and the perception of pain. Thus patients may not initially notice small wounds to legs and feet, and may therefore fail to prevent infection or repeated injury. Further, diabetes causes immune compromise and damage to small blood vessels, preventing adequate oxygenation of tissue, which can cause chronic wounds. Pressure also plays a role in the formation of diabetic ulcers.

2.      Venous and arterial ulcers
Venous ulcers, which usually occur in the legs mostly affect the elderly. They are thought to be due to venous hypertension caused by improper function of valves that exist in the veins to prevent blood from flowing backward. Ischemia results from the dysfunction and, combined with reperfusion injury, causes the tissue damage that leads to the wounds.

3.      Pressure ulcers
Another leading type of chronic wounds is pressure ulcers, which usually occur in people with conditions such as paralysis that inhibit movement of body parts that are commonly subjected to pressure such as the heels, shoulder blades, and sacrum. Pressure ulcers are caused by ischemia that occurs when pressure on the tissue is greater than the pressure in capillaries, and thus restricts blood flow into the area. Muscle tissue, which needs more oxygen and nutrients than skin does, shows the worst effects from prolonged pressure. As in other chronic ulcers, reperfusion injury damages tissue.