Diabetic Foot Ulcer

What is a diabetic foot ulcer?

A diabetic foot ulcer is a break in the skin that goes through at least the top layer and does not heal normally. Three problems combine to cause it:

• Nerve damage (neuropathy): you cannot feel a stone in your shoe, a burn or a tight shoe, so injuries go unnoticed. Damage to the motor nerves also changes foot shape, creating clawed toes and high-pressure spots.
• Poor blood flow: narrowed arteries from peripheral artery disease starve the wound of oxygen.
• Repeated pressure: walking on the same spot thickens the skin into callus, and bleeding under the callus breaks down into an ulcer.

Types of diabetic foot ulcer

Diabetic foot ulcer stages

Doctors grade ulcers to plan treatment. The Wagner scale is the best known:

Specialist clinics often use the University of Texas system or SINBAD score instead, because they also record infection and poor blood supply, which predict outcomes better.

Signs of an infected diabetic foot ulcer

Infection is present in about half of ulcers at first visit. Because diabetes blunts inflammation, signs can be subtle:

• redness, warmth or swelling around the wound
• pus or cloudy, increased drainage
• a bad smell
• new pain or tenderness
• the wound getting larger or deeper, or bleeding easily
• blood sugar that is harder to control

A diabetic foot infection can spread to bone in days. If a sterile probe touches bone at the base of the ulcer, bone infection is likely.

How doctors assess an ulcer

• Measuring the size and depth, and probing for bone
• Checking foot pulses and the ankle-brachial index or toe pressures
• Testing sensation with a 10 g monofilament
• Taking a deep tissue sample (not a surface swab) to culture bacteria when infection is suspected
• X-rays, and MRI if bone infection is possible
• Blood tests for blood sugar (HbA1c), kidney function and inflammation markers

Diabetic foot ulcer treatment

Offloading pressure

Taking weight off the ulcer is the most important step. Walking on it, even briefly, undoes healing. Options include a total contact cast or a non-removable knee-high walker, removable boots, special shoes and felt padding. Removable devices only work if you wear them for every step, including trips to the bathroom at night.

Debridement and dressings

A clinician regularly cuts away callus and dead tissue so healthy tissue can grow. Dressings keep the wound moist but not soggy and are chosen by the amount of drainage. Do not soak your foot, because it softens the skin around the wound.

Treating infection

Mild infections are treated with antibiotic tablets. Moderate or severe infections, or bone infection, may need intravenous antibiotics, surgical drainage or removal of infected bone.

Restoring blood flow

If circulation is poor, a vascular specialist may open blocked arteries with angioplasty or bypass surgery. Without enough blood flow, ulcers rarely heal.

Supporting healing

• Keep blood sugar in your target range.
• Stop smoking, which narrows blood vessels.
• Eat enough protein.
• Advanced therapies for hard-to-heal ulcers include negative pressure wound therapy, skin substitutes and hyperbaric oxygen in selected cases.

Healing time and complications

With good care, many neuropathic ulcers heal in 6 to 12 weeks. Ischemic ulcers and deep infections take longer. After healing, about 40% of people develop another ulcer within a year, so prevention continues for life.

Serious complications include spreading cellulitis, bone infection, gangrene and amputation. Having a foot ulcer is also a marker of high heart disease risk.

Preventing foot ulcers

• Check both feet every day, including between the toes and the soles. Use a mirror or ask someone to help.
• Wash and dry feet daily and moisturize the skin, but not between the toes.
• Never walk barefoot, even at home.
• Wear well-fitting shoes and check inside them for stones before putting them on.
• Have calluses and nails cared for by a podiatrist.
• Get a full foot exam at least once a year, and more often if you have neuropathy, deformity or a past ulcer.

The diabetic foot page covers wider foot risks and screening in diabetes.

Frequently asked questions

How long does a diabetic foot ulcer take to heal?

Many superficial neuropathic ulcers heal in 6 to 12 weeks with offloading and regular care. Deep, infected or ischemic ulcers can take several months. An ulcer that has not shrunk by about half after 4 weeks of good care needs a change in treatment.

What does the start of a diabetic foot ulcer look like?

It often starts as a callus with a dark spot of bleeding under it, a blister, or a small crack that does not close. Drainage on your sock may be the first sign because pain is often absent. Have any of these checked promptly.

Can a diabetic foot ulcer heal on its own?

Rarely. Without offloading and wound care, continued pressure and poor healing usually make it larger or infected. Early specialist care gives the best chance of healing and lowers the risk of amputation.

Should I let a diabetic foot ulcer air out?

No. Wounds heal faster when kept moist and covered with an appropriate dressing. Leaving the ulcer open lets it dry, crack and pick up bacteria. Follow the dressing plan from your wound care team.

When is amputation needed for a diabetic foot ulcer?

Amputation is considered when there is gangrene, a severe infection threatening life or the limb, or bone infection that cannot be controlled. Early treatment of ulcers and restoring blood flow prevent most amputations.