What Causes Venous Leg Ulcers?

A venous leg ulcer is an open sore on the lower leg or around the ankle that is slow to heal. These ulcers are usually linked to problems with the veins in the legs, rather than a problem with the arteries.

Venous ulcers can be painful, messy, and frustrating, but understanding why they happen can make the condition feel less mysterious and help you know what to do next.

At Southwest Veins, we often assist clients with untreated varicose veins that have led to the development of these ulcers.

How your leg veins are meant to work

Your leg veins have an important job. They return blood back up towards your heart, working against gravity.

They do this with help from two main features:

• One-way valves inside the veins, which are meant to stop blood from flowing backwards.
• The calf muscle pump, where your calf muscles squeeze the veins as you walk, pushing blood upwards.

When valves and muscle action work well, blood keeps moving, and pressure in the lower legs stays under control.

How long-term high pressure in the leg veins causes venous ulcers

Most venous ulcers develop because of long-term high pressure in the leg veins, often due to chronic venous insufficiency. This means the veins are not moving blood back up the leg efficiently, so blood tends to pool in the lower leg.

There are a few common reasons this happens.

1) Weak or faulty vein valves

If the valves in the leg veins become weak or damaged, blood can fall back down the vein instead of continuing upwards. This is sometimes called venous reflux. Over time, that backwards flow increases pressure in the lower leg, especially around the ankle.

Varicose veins are a common sign of valve problems, but you can have valve issues even without very visible varicose veins.

2) Blocked or damaged veins after a blood clot

A previous deep vein thrombosis, which is a blood clot in a deep vein, can leave behind scarring and damage inside the vein. Even after the clot has gone, the vein may not work normally. This can also lead to higher pressure in the veins and long-term swelling. This pattern is often referred to as post-thrombotic syndrome.

3) Poor calf muscle pumping

If you are not walking much, or you spend long periods sitting or standing still, the calf muscles do not squeeze the veins often enough. Blood can pool in the lower legs, and swelling may build up.

Reduced mobility can happen for many reasons, including joint problems, back pain, recovery after surgery, or simply finding it difficult to exercise.

How an ulcer actually forms

A venous ulcer often begins with something small. It might be a minor knock, a scratch, a shoe rub, or a patch of irritated skin that breaks down after itching.

In healthy skin, small injuries usually heal quickly. In skin affected by venous disease, healing is slower because:

• Swelling can reduce the flow of oxygen and nutrients to the skin.
• Inflammation can interfere with the normal healing process.
• The skin barrier may already be compromised by dryness or eczema.

Once the skin breaks, the area can weep fluid, become painful, and widen into an open sore. Without addressing the underlying venous pressure, the ulcer may persist or return after it has healed.

Who is more likely to develop a venous ulcer?

Venous ulcers can affect anyone, but they are more common if you have one or more risk factors, such as:

• Varicose veins or known vein valve problems
• A previous deep vein thrombosis
• Long-term leg swelling
• Previous leg ulcer, as recurrence is more likely once the skin has been damaged before
• Reduced mobility
• Spending long periods standing or sitting still
• Obesity, which can increase pressure in the leg veins and make swelling more likely
• Increasing age, as vein valves can become less effective over time
• Pregnancy history, as pregnancy can put extra strain on leg veins in some people

Having these risk factors does not mean you will develop an ulcer, but it does increase the chances, especially if swelling and skin changes are already present.

Venous ulcers and other causes of leg ulcers

Not every leg ulcer is venous. Some ulcers are caused by poor arterial circulation, diabetes related nerve and skin problems, pressure damage, or inflammatory skin conditions.

This is important because treatment differs. For example, compression is often helpful for venous ulcers, but it may be unsafe if the blood supply to the foot is significantly reduced.

That is why a proper assessment matters. In many cases, clinicians will check circulation in the legs, often using an ankle brachial pressure index test, and may arrange an ultrasound scan to assess vein function.

When to seek medical help

It is a good idea to seek medical advice if you have a wound on your lower leg that is not improving, or if you notice signs that a venous ulcer could be developing, such as worsening swelling, increasing skin discolouration, or a patch of fragile skin that keeps breaking down.

Seek urgent help if you notice any of the following:

• Increasing redness, heat, swelling, or tenderness around the wound
• Pus, a bad smell, or rapidly increasing discharge
• Fever, chills, or feeling generally unwell
• Sudden severe pain in the leg, or a leg that becomes very swollen quickly
• A foot that becomes cold, pale, blue, or numb

These can be signs of infection or circulation problems that need prompt assessment.

A reassuring note about prevention and treatment

Venous ulcers are closely linked to treatable vein problems. The most effective care usually focuses on reducing venous pressure and supporting the skin to heal.

Depending on your situation, this may include compression therapy after circulation has been checked, appropriate dressings, improving movement and calf muscle activity, leg elevation, and addressing underlying vein reflux with specialist treatment when suitable.

Concerned about a possible venous leg ulcer?

The team at Southwest Veins specialises in diagnosing and treating venous conditions using modern, minimally invasive techniques. If you have concerns about a possible venous leg ulcer or would like reassurance about your vein health, arrange a free assessment and take the next step towards healthier legs.