Chronic venous insufficiency, usually shortened to CVI, is a condition in which the veins in the legs cannot return blood to the heart efficiently. It develops when the one-way valves inside the leg veins weaken or become damaged, allowing blood to flow backward and pool in the lower leg. That pooling is what produces the familiar pattern of symptoms: legs that ache and feel heavy by afternoon, swelling around the ankles, and skin changes that appear gradually over years.
CVI is progressive. It rarely announces itself, and the early stages are easy to attribute to a long day or a demanding job. Left unmanaged it advances through stages that become harder to treat, which is why recognizing it early matters more than it might seem.
How healthy leg veins work
Blood in the legs has to travel upward against gravity. It does this through two mechanisms working together. The calf muscles contract as you walk and squeeze the deep veins, pushing blood upward, a mechanism often called the calf muscle pump. A series of one-way valves inside the veins then prevents that blood from falling back down between contractions.
When those valves fail, the system loses its ratchet. Blood refluxes downward, pressure builds in the lower leg veins, and that sustained pressure pushes fluid out into the surrounding tissue. This is called venous hypertension, and it drives nearly every symptom of CVI.
Common symptoms
- Aching, heaviness, or fatigue - typically worse at the end of the day and after long periods of standing or sitting.
- Swelling - usually starting at the ankle, often improving overnight and returning during the day.
- Visible veins - spider veins or varicose veins, which are frequently the first sign people notice.
- Cramping or restlessness at night - particularly in the calves.
- Itching or dry, irritated skin - over the lower leg and ankle.
- Skin discoloration - brownish staining around the ankle from iron deposits left by leaked blood cells.
- Hardened or thickened skin - a later change, where the tissue becomes firm and tight.
- Open sores - venous leg ulcers, usually near the ankle, representing advanced disease.
What raises the risk
Some risk factors are structural and some are situational. Family history matters a great deal, as does age, since valves lose competence over time. Pregnancy raises venous pressure and hormone levels that relax vein walls, which is why symptoms often begin or worsen during pregnancy. Occupations that involve prolonged standing or sitting reduce the calf pump's contribution. Excess weight increases abdominal pressure, which impedes venous return. And a previous deep vein thrombosis can damage valves directly, producing what is known as post-thrombotic syndrome.
How it is diagnosed
A clinician will take a history, examine the legs, and in most cases order a duplex ultrasound. That scan shows both the structure of the veins and the direction of blood flow, which is how reflux is confirmed and mapped. Mapping matters because it determines whether a procedure would help and which veins are involved.
Where compression fits
Graduated compression is the foundation of CVI management, and it is used at every stage of the condition: on its own in earlier stages, alongside procedures in later ones, and as long-term maintenance after treatment. It works by opposing venous hypertension directly: external pressure narrows the vein, helps the remaining valves close more effectively, and improves the efficiency of the calf muscle pump with every step.
For early CVI with moderate symptoms, 20-30 mmHg is the most commonly prescribed level. More advanced disease, significant swelling, or post-thrombotic symptoms often call for 30-40 mmHg. Compression does not repair damaged valves, and nothing reverses that, but consistent wear controls symptoms, slows progression, and substantially reduces the risk of skin changes and ulceration.
Consistency is the part that decides outcomes. A garment worn most days does far more than a firmer garment worn occasionally, which is why fit and comfort are clinical concerns rather than conveniences.
What else helps
- Walking - the single most useful activity, because it engages the calf muscle pump.
- Elevation - raising the legs above heart level for short periods reduces pressure and swelling.
- Calf exercises - ankle pumps and heel raises help when standing or sitting for long stretches.
- Weight management - reduces abdominal pressure and improves venous return.
- Skin care - moisturizing lower leg skin helps prevent the cracking and breakdown that precede ulceration.
- Breaking up long periods of sitting or standing - movement every half hour or so.
When to see a clinician
Any persistent leg swelling, skin discoloration around the ankle, or a sore that is slow to heal should be evaluated. Sudden swelling in one leg, particularly with warmth or pain, needs urgent assessment, as it can indicate a blood clot.
This article is general education, not medical advice. Compression is not suitable for everyone, and firmer levels should be recommended and fitted by a healthcare professional who has assessed your circulation.