Diabetic foot ulcer

What is a diabetic foot ulcer, and how common is it?

A diabetes-related foot ulcer (the clinical name) is a break in the skin of the foot, in a person with diabetes, that doesn't heal promptly¹. It can sit in the top layer of skin or go deep into the tissue of the foot².

About 3.2% of Australians living with diabetes have one³. The burden falls more heavily on Aboriginal and Torres Strait Islander people, who are up to 38 times more likely than non-Indigenous people to undergo a major amputation³.

Because ulcers are slow to heal, any new break in the skin of your foot matters if you have diabetes.

What causes it, and who is at risk?

High blood glucose over time damages nerves and blood vessels and keeps inflammation going, which slows healing⁴. That can dull the feeling in your feet and reduce their blood supply⁵.

Nerve and muscle damage can also change the shape of your feet, for example with bunions or hammertoes. Shoes can rub on these spots and break the skin, and with reduced feeling you may not notice². When nerves are damaged, the pressure of walking adds to the risk⁶.

The main risk factors are loss of feeling, poor circulation, foot deformity, a previous ulcer or amputation, longer time with diabetes, poor glucose control, smoking, kidney disease and older age⁷. These are links rather than proven causes. It helps to check that your shoes fit well and don't rub.

What does it look like, and how is it diagnosed?

The most common sign is an open sore that doesn't heal, often with redness, swelling and pain or tenderness². It can be hidden under a thick layer of discoloured skin (callus)².

A trained health professional examines the ulcer and checks for infection. Infection is identified by at least two classic signs of inflammation, or by pus, and graded as mild, moderate or severe⁸. They also check the blood supply to the foot, which helps decide what treatment may be needed, such as hospital care, scans or surgery⁸. If infection is suspected, a sample of tissue may be taken to find the germs involved⁸.

What helps first?

A foot ulcer needs professional care from the start, not home treatment.

Care is a package: taking pressure off the sore (called offloading), removing hard, dead or infected skin, dressings, treating any infection, and managing blood glucose⁴. Your podiatrist, practice nurse or other health professional usually does the skin removal and dressings, and may add a temporary pad to keep pressure off².

Offloading is arguably the most important part⁹. For a sore on the sole of the forefoot or midfoot with nerve damage, the first choice is a knee-high device you can't take off. If that isn't suitable or tolerated, a removable knee-high or ankle-high device is the next choice⁹. Casts that stay on improve healing¹⁰, but aren't suitable when infection is in the soft tissue or bone¹⁰.

Antibiotics are for infected wounds only⁸, so don't expect them for an ulcer with no sign of infection. It's worth asking which offloading device suits you.

What helps if that isn't enough?

If an ulcer isn't improving, ask for a review by a multidisciplinary foot team (health professionals from different fields working together), because these teams improve outcomes⁸. Ask for your circulation to be assessed too: a foot with poor blood supply may need an operation to restore blood flow⁸. Some ulcers that don't respond may also benefit from extra treatments chosen for them⁸.

If an infection becomes severe, an operation to clean out the wound may be needed. When the infection is very severe, part of the foot may have to be amputated so that the healthy tissue that remains can be kept¹¹.

What affects recovery, and how can I stop it coming back?

Healing is slowed by high blood glucose over time⁴ and by a reduced blood supply to the feet². Among people with an ulcer, poor circulation (peripheral arterial disease) was the strongest predictor of amputation¹². Foot ulcers are also linked with a higher risk of heart attacks and strokes¹¹, so looking after your overall health matters.

A previous ulcer raises the risk of another¹⁰, so treat your foot as higher risk after one. Keep up your yearly foot screening with a suitably trained health professional¹³, and wear shoes that fit well and don't rub.

What can make it serious?

• You have a foot ulcer or wound and also have a fever, flu-like symptoms, a high or low temperature or a fast heartbeat.
• You have diabetes or poor circulation and signs of infection in your foot, toe or nail, such as redness, warmth, swelling, pus, a bad smell or more pain.
• You have diabetes or poor circulation and a foot infection that is spreading fast, with a fever, and you feel very unwell.
• You have diabetes, poor circulation or reduced feeling in your feet and notice a new wound, sore, blister or colour change on your foot, or a sore that isn't healing.
• You have diabetes or reduced feeling in your feet and one foot becomes red, hot or swollen, or suddenly changes shape, even if it doesn't hurt (possible Charcot foot).
• You have constant pain in your foot or toes that is worse at night or when your legs are raised, and eases when you hang your leg down (this can be a sign of poor circulation).
• The skin on your toes or foot turns dark or black, or a wound turns black and smells bad.
• You have a foot wound, ulcer or infection and also feel very unwell, with confusion or slurred speech, severe shivering or muscle pain, severe breathlessness, mottled or discoloured skin, or little or no urine (possible sepsis).
• Your leg or foot suddenly turns cold and pale, with pain or numbness, or you suddenly can't move it.