Diabetic ulcers occur most often on the bottom of the foot, particularly under the ball of the foot and the big toe. They can also develop on the tips of toes, the heel, the ankle bones, and less commonly on the lower leg. The specific location depends largely on what’s driving the ulcer: nerve damage, poor blood flow, or structural changes in the foot. Between 19% and 34% of people with diabetes will develop a foot ulcer in their lifetime, and more than half of those ulcers may become infected.
The Plantar Surface: Where Most Ulcers Form
The plantar surface, or sole of the foot, is the most common site for diabetic ulcers. These ulcers develop in weight-bearing areas where pressure concentrates during walking. The metatarsal heads (the bony bumps at the ball of the foot) and the underside of the big toe are the highest-risk zones because they absorb the most force with every step.
The heel is another frequent location. Any bony prominence on the bottom of the foot can become an ulcer site when nerve damage prevents you from feeling the repetitive pressure and friction that would normally cause pain. Without that pain signal, there’s no instinct to shift your weight or stop walking, and tissue breaks down over days or weeks without you noticing.
How Nerve Damage Determines Location
Diabetic neuropathy is the primary reason ulcers form where they do. It affects three types of nerves, and each contributes differently to ulcer risk.
Sensory nerve damage is the most direct cause. When you lose feeling in your feet, you can’t detect sharp objects, hot surfaces, or the friction from a poorly fitting shoe. A blister or small wound goes unnoticed and worsens. Motor nerve damage plays a subtler role: it weakens the small muscles in the foot, causing the toes to curl or claw. This shifts pressure to new areas, like the tips of the toes or the tops of bent joints, creating pressure points that wouldn’t exist in a normally shaped foot. Autonomic nerve damage reduces sweating, leaving the skin dry and prone to cracking, which opens the door to infection.
The combination matters. A foot with both sensory loss and structural deformity concentrates force on a small area of skin that can’t feel the damage happening. That’s why ulcers so reliably appear over bony prominences rather than in soft, cushioned areas.
How Poor Blood Flow Shifts Ulcer Sites
When peripheral artery disease is the main problem rather than neuropathy, ulcers tend to appear in different spots. Ischemic ulcers, caused by insufficient blood supply, favor the tips and edges of the toes. In one study of elderly diabetic patients, 68.5% of those with ischemic ulcers had them at the extremities of the toes. The lateral border of the foot and the spaces between toes are also common.
These locations make sense physiologically. The toes are the farthest point from the heart, and when arteries narrow, they’re the first to be starved of oxygen. Even minor trauma to an area with poor circulation can become an ulcer because the tissue lacks the blood supply needed to heal. Ischemic ulcers often look different from neuropathic ones: they tend to be painful, have a pale or dark wound bed, and the surrounding skin may feel cool to the touch.
Ulcers Beyond the Foot
While the vast majority of diabetic ulcers occur below the ankle, people with diabetes are also prone to ulcers on the lower leg, especially when venous insufficiency or arterial disease is involved. Arterial ulcers commonly appear over the lateral malleolus (the bony bump on the outside of the ankle), the shin, and other bony prominences of the lower leg. Venous ulcers, driven by poor blood return in the veins, cluster around the inner ankle and the lower third of the calf, a region called the gaiter area. Roughly 95% of venous ulcers form in this zone.
An ulcer above the mid-calf in a diabetic patient is likely caused by something other than the typical diabetic or vascular mechanisms and warrants a closer look at other possible causes.
Structural Deformities Create New Risk Zones
Charcot neuroarthropathy is a condition where nerve damage leads to weakening and collapse of the bones in the foot, most often in the midfoot. This creates a “rocker-bottom” deformity that shifts weight-bearing to an area of the foot not designed for it. In a study of patients with Charcot midfoot deformity, 48% developed a plantar midfoot ulcer, an area that rarely ulcerates in people with normal foot structure.
Bunions, hammertoes, and other common deformities also redirect pressure. A hammertoe can lead to an ulcer on the top of the bent toe joint where it rubs against a shoe, or at the tip of the toe where it presses into the ground. Any change in foot shape that creates a new pressure point is a potential ulcer site in someone who can’t feel the warning signs.
Pre-Ulcerative Signs to Watch For
Ulcers don’t appear without warning. Several visible skin changes signal that tissue is under stress and an ulcer may be forming. Calluses are the most common pre-ulcerative lesion. A callus on the bottom of the foot tells you that area is absorbing excessive pressure, and if the callus thickens and the pressure continues, the tissue beneath it can break down into an open wound.
Other warning signs include ingrown toenails, fungal infections, blisters, deep cracks (fissures) in dry skin, and small hemorrhages beneath a callus. Any of these can become the entry point for an ulcer, particularly when sensation is reduced and the problem goes unaddressed. Regular foot checks, either by yourself or a care provider, are one of the most effective ways to catch these changes early.
Why Recurrence Is So Common
Once a diabetic ulcer heals, the same spot remains vulnerable. The underlying nerve damage, blood flow problems, and structural deformities don’t go away when the wound closes. About 40% of people who heal a foot ulcer develop another one within a year. That number climbs to roughly 60% within three years and 65% within five years.
Recurrence tends to happen at or near the original site because the mechanical forces and tissue weakness that caused the first ulcer persist. Scar tissue is less resilient than normal skin, and the area may have altered blood supply from the healing process. This is why ongoing pressure relief through therapeutic footwear, custom insoles, and regular monitoring remains important long after a wound has closed.