Swollen Legs: When to Relax and When to Worry. Causes, Tests and Treatment Explained

Leg swelling is not always a scary thing

Most leg swelling is harmless. It often comes from standing or sitting for long periods, hot weather, a salty diet, or simply not moving enough. Not all swellings are the same, though: some point to a blood clot, an infection or a problem with the heart, kidneys or liver that needs prompt attention.

Swelling after surgery is a good example. After a knee operation such as ACL reconstruction, swelling around the knee can last 3 to 4 months, and after a knee replacement it can persist for a year or more. Having swelling does not mean something is wrong.

Doctors call this swelling oedema: extra fluid that collects in the tissues. Gravity pulls it to the feet, ankles and lower legs. A useful first question is whether it affects one leg or both:

• One leg usually points to a local cause in that leg, such as an injury, a clot, an infection or a vein or lymph problem.
• Both legs more often point to a general health cause, such as medicines, the heart, kidneys, liver or thyroid, or simply prolonged standing.

Seek emergency help (call 108 or go to the nearest emergency department) if leg swelling comes with:

• Sudden breathlessness, chest pain, coughing blood, or feeling faint (possible clot in the lung)
• A painful, swollen calf or thigh in one leg, especially after surgery, a plaster cast, a long journey or bed rest
• A red, hot, rapidly spreading area of skin with fever
• Swelling with a cold, pale or blue foot
• Sudden swelling of the face, hands and legs in pregnancy, with headache or blurred vision

Harmless or needs attention?

Usually harmless	See a doctor soon (within days)	Urgent (same day / emergency)
Both ankles puffy by evening, gone by morning	Swelling that lasts more than a week or keeps returning	One calf or thigh suddenly swollen, painful or tight
After long standing, a long flight or bus journey, or hot weather	Swelling with weight gain, tiredness or breathlessness on exertion	Swelling with breathlessness or chest pain
Mild swelling in late pregnancy without other symptoms	Swelling after starting a new medicine	Red, hot, spreading skin with fever
Swelling around the knee or ankle that is slowly improving after surgery or a sprain	Swelling that pits deeply when pressed, or skin changes and darkening around the ankles	Swelling after surgery that suddenly worsens, with calf pain, wound redness or discharge
Mild swelling with a known minor injury	One leg slowly getting larger over months	Swelling with a cold, pale foot, or after a major injury

A simple check: press a thumb firmly into the swollen area for 5 seconds. If a dent remains, it is pitting oedema, typical of fluid build-up. Swelling that does not pit, with firm, thickened skin, suggests lymphoedema.

Local causes: usually one leg

Cause	Typical features	How serious
Injury (sprain, fracture, muscle tear)	Swelling, bruising and pain after a clear injury	Usually settles; X-ray if you cannot bear weight
Deep vein thrombosis (DVT)	One calf or thigh swollen, tender, warm; pain on walking; often after surgery, a cast, travel or bed rest	Urgent: a clot can travel to the lungs
Cellulitis (skin infection)	Red, hot, tender, spreading skin, often with fever; common in people with diabetes or cracked heels	Urgent: needs antibiotics
Ruptured Baker's cyst	A cyst behind the knee bursts, causing sudden calf pain and swelling that mimics DVT	Not dangerous itself, but needs a scan to rule out DVT
Varicose veins and chronic venous insufficiency	Swelling worse by evening, aching, visible veins, darkened skin around the ankle, sometimes ulcers	Not urgent but progressive; worth treating
Post-thrombotic syndrome	Long-term swelling and aching in a leg that had a DVT	Chronic; managed with compression
Lymphoedema	Firm swelling that starts at the foot, includes the toes and does not pit easily	Chronic; needs specialist management
Filarial lymphoedema ("hathi paon" or elephantiasis)	Gradual, firm swelling of one or both legs in people from endemic areas, sometimes with recurrent fevers and skin infections	Chronic; India has an estimated 620,000 lymphoedema cases (AJTMH, 2026)
Arthritis or joint effusion	Swollen, stiff knee or ankle, worse after activity	Usually not urgent; a hot, red joint with fever needs same-day review
Compartment syndrome	Severe, increasing pain and tightness after a major injury or fracture, worse when the toes are moved	Emergency

General health causes: usually both legs

Cause	Typical features	What to do
Prolonged standing or sitting, heat, inactivity	Both ankles puffy by evening, better overnight	Harmless; move regularly and raise your legs
Salt and diet	High salt intake, packaged and fried foods	Reduce salt
Low protein or anaemia	Poor diet, weight loss, tiredness	Blood tests; treat the cause
Medicines	Starts after a new tablet	Discuss with your doctor; never stop medicines on your own
Heart failure	Swelling with breathlessness on exertion or lying flat, tiredness, weight gain	See a doctor promptly
Kidney disease (including nephrotic syndrome)	Puffy eyes in the morning, foamy urine, swelling of legs	Urine and blood tests
Liver disease	Swelling with a swollen tummy (ascites), yellow eyes, often with alcohol use	See a doctor promptly
Underactive thyroid	Tiredness, weight gain, feeling cold, dry skin, firm swelling	Thyroid blood test
Pregnancy	Mild ankle swelling in the third trimester is common	Sudden swelling with headache, vision changes or high blood pressure can signal pre-eclampsia and is urgent
Obesity	Swelling from pressure on leg veins and lymphatics	Weight reduction and exercise

Medicines that commonly cause ankle swelling

• Amlodipine and similar blood pressure tablets (calcium channel blockers): in a meta-analysis, the risk of swelling was about three times higher than with placebo, and higher at 10 mg than at 2.5–5 mg (Vukadinović et al., 2019). A lower dose or a different medicine often helps.
• Anti-inflammatory painkillers (NSAIDs) such as diclofenac and ibuprofen
• Steroids such as prednisolone
• Some diabetes medicines (pioglitazone) and hormones (oestrogen, the contraceptive pill)
• Some nerve pain medicines (pregabalin, gabapentin)

Swelling after surgery: what is normal

Swelling is part of normal healing after any leg operation. Bleeding into the tissues, inflammation and reduced muscle pumping all add to it, and gravity often moves the swelling and bruising down to the shin, ankle and foot.

Operation	What to expect
Knee arthroscopy (meniscus surgery)	Swelling peaks in the first few days and settles over 2–6 weeks
ACL reconstruction	Knee swelling for 3–4 months, worse after activity; ankle swelling in the first weeks is common
Total knee replacement	Peaks in the first 2 weeks and improves steadily, but mild swelling can last a year or more. In one study, only 28% of patients were back to their pre-operative knee size at 2 years, and the remaining swelling did not affect function (Barton et al., AAOS 2026)
Fracture fixation (ankle, tibia, elbow)	Swelling for 3–6 months, often worse by evening

What is not normal after surgery

• A sudden increase in calf swelling, pain or tightness, especially in one leg. After ACL reconstruction, symptomatic DVT affects about 1 in 100 patients, mostly within 30 to 90 days (Forsythe et al., 2022). Risk is higher with age over 45, smoking, previous clots, hormone use and long operations.
• Breathlessness or chest pain: an emergency.
• Wound redness, warmth, discharge or fever: possible infection.
• Swelling that keeps getting worse rather than gradually better, or a hot, very tense knee.

After surgery, follow the clot-prevention plan your surgeon gives you, such as early walking, calf pumps, stockings or blood-thinning medicine.

Investigations

Your doctor chooses tests based on the history and examination, so not everyone needs all of these:

Test	What it looks for
Examination	One or both legs, pitting, skin changes, tenderness, pulses, heart, lungs and abdomen
Venous Doppler ultrasound	Blood clots (DVT), varicose veins and faulty vein valves
D-dimer blood test	Helps rule out a clot when the risk is low; often raised after surgery, so less useful then
Blood tests	Blood count, kidney and liver function, protein (albumin), thyroid, blood sugar
Urine test	Protein leakage from the kidneys
ECG, echocardiogram, BNP	Heart function when heart failure is suspected
X-ray or MRI	Fractures, arthritis, Baker's cyst or other joint problems
Night blood test or antigen test for filaria	Filarial infection in people from endemic areas
Lymphoscintigraphy	Lymphatic drainage, when lymphoedema is suspected

Treatment and self-care

Treatment targets the cause. Alongside that, these simple steps help most kinds of swelling:

1. Elevate your legs above heart level for 20–30 minutes several times a day
2. Keep moving: walking and ankle pumps activate the calf muscle pump that pushes fluid back up the leg
3. Avoid long periods of standing or sitting still; on long journeys, get up or flex your ankles every hour
4. Cut down on salt and keep a healthy weight
5. Compression stockings for venous problems, lymphoedema and after some operations, but only after a doctor has checked your circulation, because they are unsafe with poor arterial blood flow
6. After surgery: ice and elevation, regular gentle exercise and following your rehab plan

Cause-specific treatment

Cause	Main treatment
DVT	Blood-thinning medicine, usually for at least 3 months
Cellulitis	Antibiotics, rest and elevation; foot care to prevent recurrence
Varicose veins	Compression; laser, foam or surgical treatment if needed
Lymphoedema and filarial lymphoedema	Daily skin hygiene, leg exercises, elevation, compression and prompt treatment of infections; anti-filarial medicines under the national programme
Heart, kidney, liver or thyroid disease	Treating the underlying condition; diuretics (water tablets) where appropriate
Medicine-related swelling	Dose change or an alternative medicine, decided by your doctor
Post-surgical swelling	Ice, elevation, exercise and time

Outlook

• Gravity, heat and activity-related swelling: resolves fully with simple measures.
• Post-surgical swelling: settles gradually over weeks to months; lingering mild swelling after knee replacement is common and usually harmless.
• DVT: most clots resolve with treatment, but a significant minority of people develop some long-term swelling or aching (post-thrombotic syndrome), so compression and activity matter.
• Venous insufficiency and lymphoedema: long-term conditions that can be well controlled but need ongoing care to prevent skin damage and infection.
• Heart, kidney and liver causes: depend on the underlying illness; leg swelling often improves quickly once it is treated.

Frequently asked questions

Is leg swelling dangerous? Usually not. Swelling in both ankles that comes on by evening and goes overnight is common and harmless. Sudden swelling of one leg, or swelling with breathlessness, chest pain, fever or red, hot skin, needs urgent attention.

How long does swelling last after ACL surgery? Knee swelling commonly lasts 3 to 4 months, especially after activity. It should steadily improve. A sudden increase in calf pain or swelling needs checking for a blood clot.

How long does swelling last after knee replacement? It peaks in the first 2 weeks and improves markedly by 3 months, but mild swelling can last a year or more and is usually harmless.

Why is my foot swollen after knee surgery? Gravity draws fluid and bruising down from the knee to the ankle and foot. Elevation and ankle pumps help.

Can blood pressure tablets cause swollen ankles? Yes. Amlodipine and similar medicines are a common cause, especially at higher doses. Speak to your doctor rather than stopping the medicine.

How can I tell if it is a blood clot? A clot usually causes one-sided calf or thigh swelling with pain, tenderness and warmth. Only an ultrasound scan can confirm it, so seek same-day medical review.

Can filariasis cause leg swelling? Yes. Lymphatic filariasis, spread by mosquitoes, is a major cause of long-term leg lymphoedema in parts of India. Early care and the national mass drug programme help limit it.

Do compression stockings help? They help vein problems, lymphoedema and some post-surgical swelling, but should be fitted after your doctor has checked your circulation.

The bottom line

Most leg swelling is harmless and settles with movement, elevation and less salt. Swelling after knee surgery is expected and can last months. The swellings that need attention are sudden one-sided swelling, swelling with breathlessness or chest pain, red and hot skin with fever, and swelling that keeps getting worse. When in doubt, get it checked: a simple examination and an ultrasound can rule out the serious causes quickly.

If you have swelling after an injury or orthopedic surgery, book a review with our team at Sports Orthopedics Institute, HSR Layout, Bengaluru. For swelling linked to the heart, kidneys, liver or thyroid, your physician is the right first contact.

This article is for general information and does not replace a personal consultation with a qualified doctor.

References

1. Forsythe B, et al. Incidence and risk factors for symptomatic venous thromboembolism following ACL reconstruction. Knee Surg Sports Traumatol Arthrosc. 2022;30(5):1552–1559.
2. Erickson BJ, et al. Rates of deep venous thrombosis and pulmonary embolus after ACL reconstruction: a systematic review. Sports Health. 2015;7(3):261–266.
3. Thromboprophylaxis after ACL reconstruction: controversies and future challenges. Medicina. 2026.
4. Barton K, et al. Post-operative swelling did not return to preoperative levels in most patients two years after total knee arthroplasty. AAOS 2026.
5. Vukadinović D, et al. Peripheral edema and headache associated with amlodipine treatment: a meta-analysis of randomized, placebo-controlled trials. J Hypertens. 2019.
6. Multistakeholder consultations on lymphatic filariasis elimination in India. Am J Trop Med Hyg. 2026.