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Why diabetes affects the feet
The feet are the part of the body most vulnerable to the long-term effects of diabetes. Two distinct processes combine to make foot problems in diabetes both more likely and more dangerous than they would be in someone without the condition.
Diabetic neuropathy
High blood glucose over time damages the small nerves in the feet. The result is loss of sensation: the protective pain response that would normally tell you a shoe is rubbing or that you have stood on something sharp. Injuries happen without being felt, and can become serious before they are noticed.
Diabetic ischaemia
Diabetes accelerates atherosclerosis in the arteries of the leg and foot, reducing blood flow. Without adequate circulation, wounds cannot heal, infections cannot be fought effectively, and tissues can die. Diabetic arterial disease often affects the smaller vessels below the knee, making it harder to treat than standard peripheral arterial disease.
Many people with diabetic foot problems have both neuropathy and ischaemia together, which significantly worsens the prognosis. Around 1 in 4 people with diabetes will develop a foot ulcer at some point in their lives. Diabetes is responsible for more than half of all non-traumatic lower limb amputations in the UK, the vast majority of which are preventable with timely care.
What symptoms should you look out for?
Because nerve damage can remove the sensation of pain, you may not feel that something is wrong even when there is a significant problem developing. This is why daily visual inspection of both feet is so important.
Signs to look for when inspecting your feet include:
- Any new break in the skin, cut, blister or sore, however small
- Redness, swelling or warmth in any part of the foot or lower leg
- Discharge or an unusual smell from the foot
- Black discolouration of a toe or part of the foot
- A callus or hard skin area that has become soft or broken in the centre
- A toe or foot that feels significantly colder than the other side
- Any new pain or burning in the feet, which may suggest nerve damage even if sensation is generally reduced
If you cannot see the soles of your feet clearly, use a mirror or ask someone to check for you. Never assume a small sore will heal on its own in a diabetic foot.
⚠ Red flags: get urgent same-day assessment
- Fever, or feeling generally unwell with a foot problem
- Spreading redness, swelling or warmth around a wound
- Black or darkening skin on the toes or foot
- A new ulcer, break in the skin, or pus or discharge
- Severe pain, or a foot that is cold, pale or blue
These can be signs of serious infection or loss of blood supply. Attend A&E or contact your diabetic foot team the same day.
When to seek medical attention
The speed of referral for diabetic foot problems is critical. NICE NG19 is explicit on this:
- Limb-threatening or life-threatening problems: refer immediately to A&E and inform the multidisciplinary foot care team the same day
- All other active diabetic foot problems (any new ulcer, infection, swelling or skin change): refer to the specialist multidisciplinary foot care service within 1 working day, with triage by the team within a further 1 working day
Do not wait for the next routine diabetic review. A foot ulcer that appears small or superficial can deteriorate rapidly in a person with diabetes, particularly if there is any degree of arterial disease present.
The multidisciplinary foot care team
Diabetic foot disease is complex and requires multiple specialists working together. The standard of care for active diabetic foot problems is a multidisciplinary team (MDT) that includes specialists in diabetology, podiatry, vascular surgery, orthopaedic surgery, microbiology and wound care.
The vascular surgeon's role within this team is to assess blood supply to the foot using Doppler ultrasound and ankle-brachial pressure index (ABPI) measurement, and to plan and perform revascularisation where the arteries are narrowed or blocked. Restoring blood flow is often the critical factor that allows a wound to heal.
Studies consistently show that centres with a dedicated MDT approach achieve significantly lower major amputation rates than those without, with some UK centres demonstrating reductions of over 60% following MDT implementation.
Understanding diabetic foot ulcers
A diabetic foot ulcer is a break in the skin of the foot that fails to heal within the expected time. Ulcers develop most commonly over pressure points: the ball of the foot, beneath the toes, or on the tips of the toes when they are deformed (as in hammer toes or claw toes).
The IWGDF 2023 guidelines classify foot ulcers using systems that assess depth, infection and ischaemia together, the most widely used being the WIfI classification (Wound, Ischaemia, Foot Infection). This standardises communication between teams and helps predict which patients are at highest risk of amputation, guiding the urgency of intervention.
Infection in the diabetic foot
Infection is a common and serious complication of diabetic foot ulcers. Because the immune response is impaired in diabetes, infections can spread rapidly through soft tissue and into bone (osteomyelitis). Signs of infection include increasing redness and warmth around an ulcer, swelling, discharge, foul odour, and feeling systemically unwell.
NICE NG19 recommends starting antibiotic treatment as soon as possible once infection is clinically suspected, with microbiological samples taken before or as close as possible to the start of antibiotics. The choice of antibiotic depends on the severity of infection and local resistance patterns.
Osteomyelitis (bone infection) is present in up to 20% of diabetic foot infections. It can often be treated with prolonged antibiotics, but surgical debridement or limited bone removal is sometimes necessary.
Ischaemia and the neuroischaemic foot
When poor blood supply is a significant component of a diabetic foot ulcer, healing becomes very difficult without restoring circulation. The neuroischaemic foot combines both nerve damage and arterial disease and is among the most challenging clinical presentations in vascular surgery.
Assessment of blood supply includes ABPI measurement, Doppler ultrasound, and, when revascularisation is being considered, CT angiography or MR angiography of the arteries from the aorta to the foot. Toe pressure measurement is often needed in addition to ABPI in diabetic patients, because calcified arteries can give a falsely elevated ABPI reading.
Treatment of diabetic foot ulcers
Offloading pressure
The most important local treatment for a neuropathic plantar ulcer is removing pressure from it entirely. Without offloading, even the best wound care cannot achieve healing. The gold standard is a total contact cast or irremovable offloading boot, which distributes weight away from the ulcer with every step. Removable boots are an alternative but are less effective because patients tend to remove them when they feel inconvenient.
IWGDF 2023 guidelines recommend irremovable offloading as the first-line treatment for plantar neuropathic foot ulcers in people with diabetes who can walk.
Debridement and dressings
Regular debridement (removal of dead and infected tissue) is essential to allow healthy tissue to grow. This is typically performed by a specialist podiatrist or surgeon. The appropriate dressing depends on the wound characteristics: moisture level, depth, presence of infection and the degree of ischaemia. There is no single dressing type that has been shown to be superior for all diabetic foot ulcers.
Revascularisation
When imaging shows significant arterial narrowing contributing to the failure of a diabetic foot ulcer to heal, restoring blood flow is a priority. Without adequate perfusion, no amount of wound care or antibiotics can achieve healing.
Revascularisation options include angioplasty (balloon widening of narrowed arteries, often in the tibial vessels below the knee) and bypass surgery. In diabetic patients, the pattern of disease often involves the smaller arteries below the knee supplying the foot directly. Techniques such as pedal arch angioplasty (opening up the small arteries at the level of the foot) are increasingly used at specialist centres to restore direct flow to the heel and forefoot in patients with critical ischaemia.
The decision between endovascular and open surgical revascularisation is made on the basis of anatomy, patient fitness and the availability of suitable vein conduit for bypass.
Metabolic and systemic optimisation
Blood glucose control is critical throughout treatment. Elevated glucose impairs every aspect of wound healing: immune function, collagen synthesis and tissue perfusion. Target HbA1c should be discussed with the diabetology team as part of the MDT management plan.
Blood pressure control, treatment of anaemia, nutritional support and cessation of smoking are all important adjuncts that significantly affect the likelihood of wound healing.
Preventing diabetic foot problems
The most powerful tool against diabetic foot complications is prevention. The following measures substantially reduce the risk of foot ulcers and amputations:
- Daily foot inspection: check both feet every day for cuts, blisters, redness, swelling or any skin change. Use a mirror for the soles
- Well-fitting footwear: wear shoes that do not rub, with adequate toe space. Have feet measured professionally if possible. Never walk barefoot
- Annual diabetic foot check: attend your NHS annual foot review. This should include neuropathy testing (10g monofilament), pulse assessment and ABPI if indicated
- Prompt action: seek medical attention for any new foot problem within 24 hours rather than waiting to see if it improves
- Skin and nail care: keep skin moisturised, avoid cutting nails too short and see a podiatrist rather than treating corns or hard skin yourself
- Good blood glucose and blood pressure control: these slow the progression of both neuropathy and vascular disease
- Stop smoking: smoking dramatically accelerates arterial disease in the feet
What to do next
If you have diabetes and are concerned about your feet, do not wait for symptoms to become severe. A prompt assessment including neuropathy testing and vascular examination can identify problems before they become complex.
If you have an active foot problem, do not delay: contact your GP, diabetic foot team or go to A&E depending on the urgency described above.
Sources and further reading
- NICE NG19. Diabetic foot problems: prevention and management.
- IWGDF Guidelines on the prevention and management of diabetes-related foot disease.
- NHS. Diabetic foot care.