CVI, or chronic venous insufficiency, is a condition where blood in your leg veins has trouble flowing back up toward your heart. It affects roughly 20% to 25% of adults worldwide, and over 25 million people in the United States. The condition ranges from cosmetic spider veins to painful, open wounds on the lower legs, and it tends to get progressively worse without treatment.
How Blood Flow Goes Wrong
Your leg veins contain one-way valves that keep blood moving upward against gravity. In CVI, those valves weaken, lose their shape, or stop closing properly. When they fail, blood flows backward and pools in the lower legs, a process called venous reflux. Over time, this backward flow builds up pressure in the veins, a state known as venous hypertension.
The problem can start in different parts of the venous system. Sometimes the valves in the superficial veins (closer to the skin surface) weaken on their own. Sometimes the connecting veins between the deep and superficial systems fail, letting high-pressure blood flood into smaller veins that aren’t built to handle it. That extra pressure stretches the vein walls, which in turn prevents nearby valves from closing fully, creating a worsening cycle. The sustained high pressure eventually damages the smallest blood vessels in the skin and tissue, causing the visible changes most people associate with the condition.
Who Gets CVI
CVI becomes more common with age and affects women more often than men, likely because of hormonal shifts and the effects of pregnancy on the venous system. Obesity is a major contributor: a BMI over 30 significantly raises your risk, and a BMI over 40 is strongly linked to the condition developing on its own rather than from an injury or surgery. Family history plays a clear role as well.
Occupations that require standing for long stretches, such as teaching, bus conducting, or police duty, are well-documented risk factors. A history of leg injuries, previous blood clots, or prior vein procedures also increases vulnerability. Tall stature is an independent risk factor, likely because blood has farther to travel against gravity.
Symptoms at Each Stage
Doctors classify CVI on a scale from C0 to C6, each stage reflecting visible and measurable changes in the legs:
- C0: No visible signs, though you may still have aching or heaviness.
- C1: Spider veins or small, visible veins under 3 mm wide appear on the skin.
- C2: Varicose veins, meaning bulging veins 3 mm or larger, become visible.
- C3: Swelling (edema) develops in the lower leg, often worse at the end of the day.
- C4a: The skin starts to change color, turning brown or reddish, or develops eczema-like irritation.
- C4b: The skin and tissue beneath it harden and thicken, or pale, scar-like patches form near the ankles.
- C5: A venous ulcer has formed and healed, leaving scarring.
- C6: An active, open venous ulcer is present.
Most people first notice CVI as heavy, aching legs that feel worse after standing and better after elevating their feet. Swelling that comes and goes is an early warning. The skin changes at C4 and beyond often catch people off guard because they don’t connect darkened or itchy skin near the ankles with a vein problem, but those changes signal that tissue damage is underway.
How CVI Is Diagnosed
The standard diagnostic tool is a duplex ultrasound, a painless scan that lets a technician watch blood flow through your veins in real time. They’ll look for backward flow (reflux) after squeezing or releasing the calf. If blood flows in the wrong direction for more than half a second, that’s generally considered abnormal, though some labs use a threshold of one second or longer. The test can pinpoint exactly which veins and valves are failing, which matters for planning treatment.
Compression Therapy
Graduated compression stockings are the first-line treatment for nearly every stage of CVI. These stockings apply the most pressure at the ankle and gradually less pressure up the leg, helping push blood back toward the heart. They come in different pressure levels measured in millimeters of mercury (mmHg):
- Low compression (under 20 mmHg): Suited for mild symptoms like spider veins and early swelling.
- Medium compression (20 to 30 mmHg): Effective for moderate symptoms including varicose veins and persistent edema.
- High compression (30 mmHg and above): Used for advanced disease and venous ulcers.
A trial of 125 women with early-stage CVI found that even relatively light stockings (10 to 15 mmHg) significantly reduced leg pain and improved quality of life compared to placebo stockings. A meta-analysis of 11 trials confirmed that stockings in the 15 to 20 mmHg range meaningfully reduce edema and symptoms compared to no compression or very low compression. For venous ulcers, higher-pressure stockings in the 30 to 40 mmHg range are more effective at healing wounds and preventing them from coming back. The general principle is that the highest compression level you can comfortably wear and put on consistently will give you the best results.
Procedures for More Advanced CVI
When compression alone isn’t enough, or when large varicose veins are driving the problem, procedures to close or remove the damaged veins can be highly effective. The two most common minimally invasive options use heat delivered through a thin catheter inserted into the vein: radiofrequency ablation (RFA) and endovenous laser ablation (EVLA).
Both techniques work by sealing the faulty vein shut from the inside, rerouting blood through healthier veins. A meta-analysis covering over 12,000 treated legs found success rates of 84% for radiofrequency and 94% for laser ablation, both outperforming traditional surgical stripping (78%) and foam injection therapy (77%). Individual studies report even higher short-term closure rates, some reaching 99%. These minimally invasive approaches also result in less pain, fewer complications, and faster recovery than open surgery.
Recovery is quick. In one study, patients were walking within two hours of the procedure. Most returned to normal daily activity within a week, and all within 10 days. Skin burns are uncommon, occurring in about 1.3% of radiofrequency patients and 2.6% of laser patients.
Why Venous Ulcers Are a Serious Concern
The most feared complication of untreated CVI is a venous leg ulcer, an open wound typically forming near the ankle. These ulcers are notoriously difficult to manage, not because they won’t heal initially, but because they keep coming back. Research tracking ulcer recurrence found that 22% of healed ulcers returned within three months, 57% within a year, and 78% within three years.
Those numbers explain why ongoing compression therapy after ulcer healing is so important. The recurrence rates drop significantly when people continue wearing high-compression stockings consistently. Addressing the underlying vein problem with ablation or another procedure further reduces the chances of a new ulcer forming. CVI at this stage requires long-term management rather than a one-time fix.
Lifestyle Changes That Help
Beyond compression and procedures, several daily habits make a real difference. Elevating your legs above heart level for 15 to 30 minutes several times a day reduces the pressure buildup. Regular walking activates the calf muscles, which act as a natural pump to push blood upward. Losing weight, particularly for those with a BMI over 30, directly reduces the force working against your veins. Avoiding long periods of standing or sitting without movement helps prevent blood from pooling. These changes won’t reverse valve damage that’s already happened, but they slow progression and reduce symptoms at every stage of the disease.