Veins carry blood back up the leg against gravity. When the one-way valves inside them stop closing properly, pressure builds in the lower leg — and that pressure is what produces heavy legs, evening swelling, itching, brown staining and eventually skin breakdown.
A clot is the one that cannot wait
One leg newly swollen, painful or tender when the other is not — especially over hours to days — needs assessment the same day. Sudden breathlessness, chest pain worse on breathing in, coughing blood, or fainting is 911. Around half of deep vein clots cause no symptoms at all, so a mild picture is not reassurance. More on DVT →
How leg veins are supposed to work
Blood in the leg veins has to travel upward. Three things push it: the calf muscles squeezing the deep veins with each step, the pressure of breathing, and a series of small one-way valves that stop blood falling back down between squeezes.
If those valves become leaky — after a clot, after pregnancy, with age, with long periods of standing, or simply with inherited vein wall weakness — blood refluxes downward and pressure in the lower leg rises. Sustained high venous pressure is the engine behind everything below.
What chronic venous insufficiency looks like
- Legs that feel heavy, tired or achy, worse as the day goes on and better after a night lying flat
- Swelling around the ankle that is soft and pits when pressed, improving overnight
- Visible varicose veins, or fine blue-purple thread veins around the ankle
- Itching, dry flaky skin, or eczema-like patches on the lower leg
- Brown or rust-colored staining above the ankle, from iron leaking out of blood cells into the skin
- Skin that becomes tight, firm and woody around the lower calf
- A shallow, weeping ulcer, usually on the inner ankle
The pattern is the clue: worse standing, better elevated, worse in the evening, better in the morning. That is close to the opposite of an artery problem, where symptoms come on with walking and elevating the foot makes matters worse.
What is on this side of the site
-
Venous insufficiency
The mechanism, the stages, and what treatment actually changes.
-
Stasis dermatitis
Itching, discoloration and skin changes around the ankle — what they mean and what helps.
-
DVT
Symptoms, why timing matters, and why a symptom list cannot exclude a clot.
-
Varicose veins
Where the line sits between cosmetic and clinical, and what each treatment does.
-
Venous leg ulcers
Why compression is the treatment, how they differ from arterial ulcers, and how to stop them returning.
-
Post-thrombotic syndrome
When a clot leaves lasting swelling, aching and skin change behind, and what can still be done.
-
Vein procedures
Ablation, glue, sclerotherapy and phlebectomy — what each does, and the questions to ask first.
Compression: useful, but not universal
Graduated compression is the backbone of managing venous disease, and for many people it is the single most effective thing they do. It is also the clearest example of why “poor circulation” is a dangerous shorthand: compression supports the venous system by squeezing fluid back in, and if the arterial supply into the leg is already marginal, squeezing can make the arterial problem worse.
That is why a proper assessment — usually including an ABI — comes before compression, not after. Compression safety: who needs an assessment first →
What treatment involves
- Assessment. Venous duplex ultrasound shows which veins are refluxing and whether there is any clot. An arterial check establishes whether compression is safe.
- Compression and elevation. Correctly fitted graduated compression, worn consistently, plus elevating the legs above heart level for periods during the day.
- Skin care. Emollients for the dry, fragile skin that high venous pressure produces, and prompt attention to any break.
- Movement. Walking uses the calf pump. Prolonged standing still is the hard part for many jobs, and small changes there often help more than anything bought.
- Procedures. Endovenous ablation, sclerotherapy and other techniques close refluxing veins. They are considered on symptoms and findings, not on appearance alone.
- Ulcer care. Venous leg ulcers are treated with compression bandaging by trained clinicians, alongside wound care. This is not a self-management task.
Common questions
Are varicose veins just cosmetic?
Sometimes, and sometimes not. Visible veins with no symptoms and no skin change are largely a cosmetic issue. The same veins accompanied by aching, swelling, itching, brown staining or skin thickening are a sign of sustained venous pressure, and that does progress if nothing changes.
Why is my swelling better in the morning?
Because you were lying down. Overnight, gravity stops working against the leg veins and fluid returns to the circulation. That overnight improvement is one of the more useful clues that the problem is venous rather than, say, lymphatic — lymphedema tends to improve far less with elevation once it is established.
Can I just buy compression socks online?
If a clinician has assessed your circulation and told you what strength to use, buying them yourself is reasonable. If nobody has checked, the honest answer is that you do not yet know whether compression is appropriate for your leg, and the assessment is the part that matters.
What is venous stasis?
It is a description rather than a single diagnosis — blood pooling in the lower leg because the venous system is not clearing it efficiently. It is used more or less interchangeably with chronic venous insufficiency, and the skin changes it causes are called stasis dermatitis.
Does one swollen leg always mean a clot?
No — a longstanding vein problem, a knee injury, a Baker’s cyst, cellulitis, lymphedema and several other things can do it. But a clot is on the list, it is time-sensitive, and it cannot be excluded by how the leg looks. That is why the answer to one newly swollen leg is an appointment today rather than a wait-and-see.
Where to go next
Sources
- Society for Vascular Surgery. Chronic Venous Insufficiency.
- NHS. Varicose veins.
- NHS. Leg ulcer — treatment and diagnosis.
- Centers for Disease Control and Prevention. About Venous Thromboembolism.
Written by Tom Biernacki, DPM, FACFAS. Published 20 September 2026. General education, not medical advice.