Why foot ulcers matter so much
The numbers are sobering, and they are the reason foot care occupies such a prominent place in diabetes services. A substantial minority of people with diabetes will develop a foot ulcer at some point — commonly quoted estimates put lifetime incidence in the region of one in six to one in four. Ulceration precedes the great majority of non-traumatic lower-limb amputations; the frequently cited figure is that around 85 per cent of diabetes-related amputations are preceded by a foot ulcer. The StatPearls review of diabetic foot ulceration and complications sets out the epidemiology in detail, and Diabetes UK covers the same ground for a general audience.
The encouraging half of that picture is that ulceration is substantially preventable, and that the interventions which prevent it are unglamorous and cheap: looking at the feet, wearing shoes that fit, dealing with calluses and nails safely, and getting seen quickly when something changes.
How an ulcer forms
Rarely from one cause. Typically several factors converge:
- Loss of protective sensation. Nerve damage means an injury is not felt. A stone in the shoe, a seam, a burn from a hot bath or a radiator, a blister from a new pair of shoes — none of it registers, so none of it prompts a change in behaviour.
- Repetitive pressure. Without pain to make you shift your weight, the same spot is loaded thousands of times a day. Tissue under a callus breaks down beneath the surface before the surface itself opens.
- Foot deformity. Clawed toes, a prominent metatarsal head, a collapsed arch or a previously amputated toe concentrate load in places not designed to carry it.
- Reduced blood supply. Arterial disease reduces the oxygen and nutrients available for repair, so a wound that would otherwise close simply does not.
- Impaired defence against infection. Sustained high blood glucose blunts the immune response and slows healing.
The nerve damage element is worth dwelling on. Diabetic peripheral neuropathy is usually painless — that is exactly the problem — and it develops over years without announcing itself. It can be detected in a clinic with a simple monofilament test, which takes moments and requires nothing more than a calibrated nylon filament. The NIDDK page on diabetic neuropathy describes the forms it takes.
What to look for
Because pain is often absent, the early signs are visual and circumstantial rather than symptomatic:
- A stain, discharge or blood spot on a sock or inside a shoe — frequently the very first sign.
- A callus that has darkened, has a red or black area within it, or feels boggy.
- Redness, warmth or swelling around any break in the skin.
- An unusual odour.
- A blister, crack or graze that has not closed within a couple of days.
- Any new change in the shape, colour or temperature of the foot.
Fever, spreading redness, a foul-smelling discharge or a foot that has suddenly become hot and swollen are urgent. So is a foot that is newly cold, pale or dusky, which suggests a circulation problem rather than an infection. Neither is a wait-and-see situation.
What wound care involves
Offloading is the single most important element and the one most often underestimated. A wound on the sole cannot heal while it is being walked on. Removing pressure — through a total contact cast, a removable walker, felted padding, specialist footwear or, where necessary, non-weight-bearing — does more for healing than any dressing choice. Adherence is the usual limiting factor, which is why removable devices are less effective in practice than non-removable ones.
Debridement is the removal of dead tissue and the overhanging callus rim from the wound edge. It converts a chronic wound into something closer to an acute one, allows the true size of the wound to be seen, reduces bacterial load, and is normally repeated at intervals. It is a clinical procedure and not something to attempt at home with any implement, ever.
Infection assessment and management. Not every ulcer is infected, and not every ulcer needs antibiotics. Infection is a clinical diagnosis based on the signs around the wound, not on a swab result alone — most open wounds grow organisms whether or not they are infected. Where infection is present, whether bone is involved is the question that changes the treatment plan most.
Vascular assessment. If the blood supply is inadequate, no amount of dressing changes will close the wound. Pulses, ankle pressures and, where indicated, imaging determine whether revascularisation needs to come first.
Dressings and adjuncts. Dressings maintain a moist wound environment, manage exudate and protect the wound. They are supportive rather than curative, and the evidence separating specific dressing types is much weaker than the size of the market implies. Advanced therapies — skin substitutes, negative pressure, growth factor preparations — have a place in selected wounds under specialist supervision, and are not a substitute for offloading and blood supply.
Glycaemic and general management. Blood glucose control, nutrition, smoking cessation and management of coexisting disease all affect healing, and all sit outside the dressing trolley.
Prevention, which is where the real gains are
For anyone with diabetes, neuropathy or arterial disease, a short daily routine prevents most of what this page describes: look at the whole foot including between the toes and the sole, using a mirror or another person if you cannot see it; wash and dry thoroughly, especially between the toes; moisturise the skin but not between the toes; never use heat sources, corn plasters or blades on your own feet; check inside shoes with your hand before putting them on; and never walk barefoot, indoors or out.
Alongside that, an annual foot check as a minimum — more often if risk is raised — and a low threshold for being seen when something changes. Practical guidance for the daily routine is on the diabetic foot page, and the wider red-flag list is on when a foot problem needs professional care.
If you have diabetes and you find a break in the skin of your foot, that is a reason to be seen promptly rather than to monitor it at home. Early assessment of foot wounds changes outcomes more reliably than almost anything that happens later.