Sores on the legs most commonly result from poor blood circulation, either in the veins or arteries. But infections, diabetes, inflammatory conditions, and even skin cancer can also cause them. About 0.3% of the general population has a venous leg ulcer at any given time, making vein-related problems the single most common cause. Understanding which type of sore you’re dealing with matters because the treatments are very different.
Vein Problems: The Most Common Cause
Veins in your legs contain one-way valves that push blood back up toward your heart. When those valves weaken or fail, blood pools in the lower legs and builds up pressure. This is called venous hypertension, and it’s the primary mechanism behind most chronic leg sores. The sustained pressure forces inflammatory cells out of the blood vessels and into surrounding tissue, gradually breaking down the skin until an open wound forms.
Venous ulcers typically appear on the inner ankle or lower calf. The skin around them often looks discolored, brownish, or hardened before the sore itself opens up. They tend to be shallow, irregularly shaped, and weepy rather than dry. You might also notice swelling in the leg that gets worse as the day goes on and improves overnight.
The standard treatment is compression therapy, which uses wraps or stockings that apply steady pressure (generally 30 to 50 mmHg) to counteract the pooling blood. Compression alone heals many venous ulcers, though it can take weeks to months. The catch is that compression must be used consistently, and the underlying vein problem doesn’t go away, so recurrence is common.
Artery Problems: Painful and Slower to Heal
When arteries narrow from plaque buildup (peripheral artery disease), less oxygen-rich blood reaches the lower legs and feet. Tissue that’s starved of oxygen breaks down easily, and even minor injuries can turn into sores that heal slowly or not at all. In severe cases, you may feel pain in your leg and foot even while resting, a condition called critical limb ischemia.
Arterial ulcers look and behave differently from venous ones. They tend to appear on the toes, feet, or outer ankle rather than the inner calf. The sore itself is often deeper, with well-defined edges, and the surrounding skin may feel cool to the touch or look pale. A hallmark symptom of the underlying artery disease is cramping or aching in your calf, thigh, or buttocks during walking that goes away when you stop. If you notice sores combined with that kind of exercise-related leg pain, reduced blood flow is the likely culprit.
Diabetes and Nerve Damage
People with diabetes face a compounding problem. High blood sugar over time damages both nerves and blood vessels in the legs and feet. The nerve damage (neuropathy) means you may not feel a blister, cut, or pressure sore forming. The blood vessel damage means any wound that does form heals poorly. Neuropathy alone accounts for roughly 50% of diabetic foot ulcers, reduced blood flow causes about 15%, and a combination of both drives the remaining 35%.
The lifetime risk of developing a foot ulcer if you have diabetes is about 25%. That’s a strikingly high number, and the consequences are serious: a significant proportion of people with diabetic foot ulcers eventually require amputation within four years of the initial diagnosis. These sores most often develop on the bottom of the foot or over bony areas where pressure concentrates, but they can occur anywhere on the lower leg. Because feeling is diminished, people sometimes don’t notice the sore until it’s already deep or infected.
Infections That Cause Leg Sores
Bacterial infections can either cause new sores or invade existing ones. Cellulitis, a common skin infection usually caused by streptococcus or staphylococcus bacteria, makes the skin red, swollen, warm, and painful. It can progress to blisters and open sores if untreated. MRSA, a drug-resistant form of staph, is becoming more common and can cause deeper, more aggressive skin breakdown.
Infections don’t always start on their own. Any existing wound on the leg, whether from a bug bite, a scratch, or a chronic ulcer, can become a gateway for bacteria. Signs that a leg sore has become infected include worsening pain, green or foul-smelling discharge, spreading redness around the wound edges, and fever or chills. These symptoms call for prompt medical evaluation because untreated infection can spread into deeper tissue or the bloodstream.
Inflammatory and Immune-Related Causes
Some leg sores aren’t caused by circulation problems or infections at all. Pyoderma gangrenosum is an uncommon inflammatory condition where the immune system attacks the skin, creating painful ulcers that expand rapidly. The telltale feature is a purple or violet border around the sore, with the edges appearing undermined (the wound extends beneath the surrounding skin). These ulcers can be mistaken for infected wounds or vascular ulcers, and that misdiagnosis delays proper treatment.
Vasculitis, where inflammation targets blood vessels themselves, can also cause leg sores. Because these conditions mimic other types of ulcers, they’re often diagnosed only after standard wound treatments fail. If a leg sore is growing despite appropriate care, or if it has unusual coloring or borders, an immune-related cause should be considered.
When a Sore Could Be Skin Cancer
A sore on your leg that won’t heal despite three or more months of treatment should raise concern about skin cancer, particularly squamous cell carcinoma. These cancerous ulcers can look deceptively similar to chronic wounds. Warning signs include a sore that keeps growing, changes in appearance over time, or the development of raised, fleshy tissue within the wound that doesn’t match normal healing.
In a study from Olmsted County, Minnesota, the overwhelming majority of chronic leg ulcers that were biopsied for cancer had failed to heal for more than three months. The takeaway is straightforward: a non-healing leg sore deserves a biopsy. This is a simple procedure that rules out or catches malignancy early, when it’s most treatable.
Why Self-Treating Can Backfire
It’s tempting to manage a leg sore at home with bandages and antibiotic ointment, especially if it seems minor. But research on home wound care shows that nearly half of caregivers find it challenging, and without proper knowledge, well-intentioned treatment can worsen outcomes. The risks are real: applying compression to a leg with artery disease can cut off what little blood flow remains. Keeping a wound too moist breeds bacteria. Keeping it too dry prevents healing. Using harsh antiseptics can damage healthy tissue around the wound edges.
The most important step is getting the right diagnosis. A venous ulcer, an arterial ulcer, a diabetic wound, and an inflammatory sore each require fundamentally different approaches. What helps one type can harm another. If you have a sore on your leg that hasn’t improved within two weeks, or if it’s accompanied by fever, foul smell, expanding redness, or increasing pain, getting a professional evaluation is the fastest path to healing.