A leg ulcer is a break in the skin below the knee that fails to heal within about two weeks. Most leg ulcers, around 70 to 80%, are caused by problems with the veins (venous leg ulcers), where damaged valves allow blood to pool in the lower leg. Others are caused by poor arterial blood supply (arterial ulcers), and some by a combination of both (mixed ulcers). Identifying the cause is essential because the treatment differs significantly.

Leg ulcers: venous, arterial and mixed ulcers explained

Name: Leg ulcers: venous, arterial and mixed ulcers explained
Creator: Mr Amro Elboushi
Published: 2026-05-29

What is a leg ulcer?

A leg ulcer is a break in the skin below the knee that has not healed within about two weeks. Leg ulcers are common, particularly in older people, and they can persist for months or even years if the underlying cause is not properly treated. They can be uncomfortable, affect mobility and quality of life, and sometimes become infected.

The encouraging news is that most leg ulcers heal well once the cause has been correctly identified and the right treatment started. The key is understanding what is driving the ulcer, because the three main types need very different approaches.

70 to 80%

Venous ulcers

Caused by faulty vein valves allowing blood to pool in the lower leg. The raised pressure damages the skin, usually around the inner ankle. The most common type by far.

10 to 15%

Arterial ulcers

Caused by poor arterial blood supply (peripheral arterial disease). Often painful, found on the foot, toes or outer ankle, with a punched-out appearance. Need blood supply restored.

Mixed

Mixed ulcers

A combination of both venous and arterial disease. Require careful assessment because compression therapy must be modified or avoided depending on how severe the arterial component is.

Other less common causes include diabetes (see our diabetic foot guide), pressure damage, inflammatory conditions and, rarely, skin cancer. Any ulcer that does not heal as expected should be assessed by a specialist to confirm the diagnosis.

Venous leg ulcers: the most common type

Venous leg ulcers develop when the valves in the leg veins stop working properly. Normally these valves keep blood flowing upward, back towards the heart. When they fail, blood flows backwards and pools in the lower leg (a condition called chronic venous insufficiency). The sustained high pressure in the veins damages the skin and underlying tissue, eventually causing it to break down.

Typical features of a venous ulcer include:

Location on the inner side of the lower leg, just above the ankle (the gaiter area)
A shallow wound with irregular edges
Surrounding skin that is discoloured brown or reddish (haemosiderin staining)
Itchy, flaky or inflamed skin around the ulcer (venous eczema or stasis dermatitis)
Swelling of the lower leg and ankle
Aching that tends to improve when the leg is raised

Venous ulcers are usually not severely painful unless they become infected. They are frequently associated with varicose veins and with a previous history of deep vein thrombosis (DVT).

How leg ulcers are assessed

Correct assessment is the foundation of treatment. The two essential investigations are the ankle-brachial pressure index and a duplex ultrasound scan.

The ankle-brachial pressure index (ABPI) is a simple, painless test that compares the blood pressure at the ankle with the blood pressure in the arm using a Doppler probe. It tells us how good the arterial blood supply to the leg is, which determines whether compression therapy is safe. This test must be done before any compression is applied.

A duplex ultrasound scan of the leg veins maps the venous system, confirms whether there is venous reflux (backward flow due to faulty valves), and identifies which veins are affected. This guides whether treatment of the underlying vein problem might help the ulcer heal and prevent recurrence.

What the ABPI result means for treatment

0.8 to 1.3 Normal Arteries healthy. Full compression therapy can be used safely.

0.5 to 0.8 Mixed disease Some arterial disease. Modified (reduced) compression under specialist supervision.

Below 0.5 Severe PAD No compression. Refer to vascular surgeon for assessment of blood supply.

Above 1.3 Falsely high Calcified arteries (common in diabetes). Needs specialist vascular assessment.

Why the ABPI matters so much: compression therapy is extremely effective for venous ulcers, but applying firm compression to a leg with poor arterial blood supply can cut off circulation and cause serious harm, including tissue loss. This is why no leg ulcer should be treated with compression until the arterial supply has been checked. If you have a leg ulcer and have been offered compression without an ABPI test, ask for one first.

Source: NICE CKS Venous leg ulcer (accessed 2026). Compression thresholds based on ABPI assessment.

Treating venous leg ulcers

Cornerstone of treatment

Compression therapy

Once arterial disease has been excluded with an ABPI test, compression therapy is the single most effective treatment for a venous leg ulcer. Compression, applied as multi-layer bandaging or compression stockings, counteracts the high venous pressure, reduces swelling, and dramatically improves healing rates.

The evidence is clear that high compression (around 40 mmHg at the ankle) heals venous ulcers faster than low compression. Compression must be applied by a trained practitioner, usually a community or tissue viability nurse, and is worn continuously, being changed at regular intervals depending on the system used.

With proper compression, a significant proportion of venous ulcers heal within 12 to 24 weeks. Concordance with compression is the most important factor in success.

Local care

Wound care and dressings

The ulcer itself is dressed to manage moisture and protect the wound bed. The choice of dressing is based on the amount of fluid (exudate) and the condition of the wound, rather than any single dressing being superior. The aim is a simple, comfortable dressing under the compression. Routine antibiotics or antiseptics are not recommended unless the ulcer is clinically infected.

Treating the cause

Treating the underlying vein problem

Compression treats the consequences of venous disease, but addressing the underlying cause, the faulty veins themselves, can help ulcers heal and significantly reduce the chance of recurrence. Where duplex ultrasound confirms venous reflux, keyhole procedures to close the faulty veins (such as endovenous laser ablation, radiofrequency ablation or foam sclerotherapy) are increasingly recommended.

Modern evidence supports treating venous reflux early in people with venous ulcers, as it improves both healing and long-term outcomes. See our varicose veins guide for more detail on these treatments.

Skin and symptoms

Managing skin changes and pain

The skin around a venous ulcer is often inflamed (venous eczema). This is treated with emollients (moisturisers) and, if significantly inflamed, a short course of an appropriate topical steroid. Adequate pain relief and elevation of the leg when resting are also important parts of care.

Arterial leg ulcers

Arterial ulcers are caused by inadequate blood supply to the leg due to narrowed or blocked arteries (peripheral arterial disease). Unlike venous ulcers, the priority is restoring blood flow, and compression is generally not appropriate.

Typical features of an arterial ulcer include:

Location on the foot, toes, heel or outer ankle
A deep, punched-out appearance with well-defined edges
A pale or grey wound base with little bleeding
Significant pain, often worse at night or when the leg is elevated, and relieved by hanging the leg down
A cold, pale foot with absent or weak pulses

Arterial ulcers require assessment of the blood supply with ABPI, duplex ultrasound and often CT or MR angiography. Treatment focuses on revascularisation: restoring blood flow with angioplasty or bypass surgery. See our peripheral arterial disease guide for more detail.

Mixed leg ulcers

Mixed ulcers have both venous and arterial components. They are common, particularly in older people, and require careful assessment because the treatment must balance the needs of both problems.

The degree of arterial disease, measured by ABPI, determines the approach. With moderate arterial disease (ABPI between 0.5 and 0.8), modified compression therapy at a reduced pressure (around 20 to 30 mmHg) can promote healing under specialist supervision. With severe arterial disease (ABPI below 0.5), compression must not be used until the blood supply has been improved by revascularisation. This is why mixed ulcers should always be managed with input from a vascular surgeon.

When to see a vascular surgeon

NICE guidance recommends referral to a specialist for further investigation and care in the following situations:

Diagnostic uncertainty about the cause of the ulcer
Suspected arterial or mixed disease (ABPI below 0.8 or above 1.3)
An ulcer that is not healing or shows no improvement after about 12 weeks of appropriate treatment
Large, complex or rapidly deteriorating ulcers
Recurrent ulcers
Confirmed venous reflux that may benefit from treatment of the underlying veins
Any concern about an unusual appearance that could suggest a different diagnosis such as skin cancer

Source: NICE CKS Venous leg ulcer (2026); NICE NG152 Leg ulcer infection: antimicrobial prescribing.

Preventing recurrence

Venous leg ulcers have a high recurrence rate if the underlying problem is not addressed. After an ulcer has healed, the following measures significantly reduce the risk of it returning:

Compression hosiery: wearing compression stockings long-term is the most effective way to prevent recurrence. They should be replaced regularly as they lose their elasticity
Treating venous reflux: keyhole treatment of the underlying faulty veins reduces recurrence and may remove the need for lifelong compression in some people
Skin care: keep the skin moisturised and inspect the legs regularly for early signs of breakdown
Staying active and elevating the legs: regular movement and raising the legs when resting both help venous return
Maintaining a healthy weight: excess weight increases pressure in the leg veins

What to do next

If you have a leg ulcer that is not healing, or that keeps coming back, a specialist vascular assessment can confirm the cause and put the right treatment in place. This includes an ABPI measurement and a duplex ultrasound scan of the veins, allowing a clear plan for both healing the ulcer and preventing recurrence.

Sources and further reading

NICE Clinical Knowledge Summary: Venous leg ulcers.
NICE NG152. Leg ulcer infection: antimicrobial prescribing.
NHS. Venous leg ulcer.

Author: Mr Amro Elboushi, Consultant Vascular and Endovascular Surgeon (GMC 7455049, FRCS Vascular Surgery).
Last reviewed: May 2026. Next review due: May 2027.
Basis: National and specialist guidance, as listed above.

Frequently asked questions about leg ulcers

What is a leg ulcer?

A leg ulcer is a break in the skin below the knee that fails to heal within about two weeks. Around 70 to 80% are venous (caused by faulty vein valves), some are arterial (caused by poor blood supply), and some are mixed. Identifying the cause is essential because the treatments differ significantly.

What does a venous leg ulcer look like?

A venous ulcer is typically a shallow wound on the inner lower leg just above the ankle. The surrounding skin is often brown or red discoloured, itchy or flaky, and the leg is usually swollen. Venous ulcers are not usually very painful unless infected, and aching tends to improve when the leg is raised.

How are leg ulcers treated?

Treatment depends on the cause. For venous ulcers, the cornerstone is compression therapy, but only after arterial disease has been excluded with an ABPI test. High compression heals venous ulcers faster than low compression. Arterial ulcers need the blood supply restored. Treating the underlying venous reflux helps healing and prevents recurrence.

Why is an ABPI test needed before compression?

Compression is highly effective for venous ulcers but dangerous if the leg also has poor arterial supply. The ABPI test confirms the arteries are healthy enough. An ABPI of 0.8 to 1.3 allows full compression. Below 0.8 needs modified or supervised compression. Below 0.5 indicates severe arterial disease, where compression must not be used and vascular referral is needed.

Will my leg ulcer come back?

Venous ulcers have a high recurrence rate if the underlying vein problem is not addressed. After healing, wearing compression hosiery long-term significantly reduces recurrence. Treating the underlying venous reflux with keyhole procedures can reduce it further. Without these measures, many venous ulcers return within a year.