A foot ulcer is an open sore on the skin of the foot that fails to heal, often persisting for more than a few weeks. Normal repair processes stall, leaving deeper tissues exposed and vulnerable to infection. An ulcer is not a disease itself, but a symptom representing a failure of the skin due to an underlying systemic issue. Successful treatment depends entirely on addressing the root physiological problem.
Ulcers Caused by Diabetes
Diabetes is a major contributing factor to foot ulcers, primarily through a combination of nerve damage and reduced blood flow to the small vessels. This condition, known as diabetic neuropathy, causes a progressive loss of protective sensation in the feet. Individuals may sustain minor injuries, such as cuts, blisters, or prolonged pressure from ill-fitting shoes, without ever feeling the initial pain or discomfort.
The lack of sensation means that repeated trauma to the same area goes unnoticed and untreated, allowing a minor skin break to progress into a deep ulcer. Neuropathy also affects the motor nerves, leading to muscle weakness and structural changes in the foot, such as toe deformities. These changes alter the biomechanics of the foot, creating abnormal pressure points under the ball of the foot or the toes where ulcers frequently develop.
Compounding the nerve damage, prolonged high blood glucose levels affect the circulatory system’s microvasculature. Hyperglycemia damages the tiny blood vessels (capillaries) that supply oxygen and nutrients to the skin. This microvascular disease impairs the body’s ability to mount a proper healing response.
The compromised blood supply and impaired immune function mean the wound cannot effectively receive the resources needed for repair. This creates a chronic, non-healing wound highly susceptible to bacterial infection. Diabetic foot ulcers most commonly occur on the plantar surface (sole of the foot), especially under the metatarsal heads or the heel, due to high-pressure loads during walking.
Ulcers Related to Poor Arterial Blood Flow
Ulcers resulting from poor arterial blood flow are known as ischemic ulcers, linked directly to Peripheral Arterial Disease (PAD). PAD involves the narrowing or blockage of arteries, typically due to atherosclerosis (plaque buildup). The consequence is a reduction in the delivery of oxygen-rich blood to the lower extremities.
When blood supply is severely limited, tissue is deprived of the oxygen and nutrients needed for survival, leading to ischemia. If the lack of blood flow persists, the tissue dies (necrosis), manifesting as a non-healing ulcer. These ulcers are often intensely painful, particularly at night or when the leg is elevated, since gravity is no longer assisting the limited blood flow.
Ischemic ulcers typically present with a “punched-out” appearance, featuring a pale base and well-defined borders. They commonly appear on the farthest points from circulation, such as the tips of the toes, between the toes, or on the heels. The surrounding skin may look shiny, thin, and cool to the touch, often lacking hair growth due to inadequate circulation.
Ulcers Resulting from Poor Venous Circulation
Venous ulcers (stasis ulcers) occur when veins chronically fail to efficiently return deoxygenated blood from the legs to the heart. This condition, termed venous insufficiency, results from damaged or incompetent valves inside the veins. Valve failure causes blood to pool, or stagnate, in the lower leg and foot.
The pooling of blood creates sustained, high pressure in the veins, a phenomenon known as venous hypertension. This chronic pressure forces fluid and waste products to leak out of the capillaries and into the surrounding tissue. The resulting edema, or swelling, prevents the normal exchange of oxygen and nutrients between the capillaries and the skin cells.
Over time, this impaired exchange leads to skin changes, including thickening, discoloration (hemosiderin staining), and inflammation. The compromised skin structure becomes fragile and easily breaks down from minor trauma, creating a shallow wound. Venous ulcers are typically shallow, irregularly shaped, and often produce a large amount of drainage. They are most frequently located in the gaiter area, just above the ankle.