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What causes swelling in only one leg? Related conditions and treatments

Medically reviewed by Leslie Greenberg, MD
Board-Certified Family Physician
Updated Jun 10, 2024  •  Published Jan 18, 2024
Fact Checked
In this article:

Overview: What does swelling in only one leg look and feel like?

Leg swelling in one leg can be alarming, especially if the swelling is very pronounced or happens quickly. It’s something to get very concerned about. That's important because most of the reasons for isolated leg swelling require medical evaluation. Some causes of leg swelling are important and can evolve into more serious problems unless taken care of quickly. Like many symptoms, leg swelling can be overwhelmingly obvious or subtle. The swelling may be limited to one area on the leg, like the calf, ankle, or knee. The whole lower leg might swell feet and all. Worse, the entire leg could swell up. The swelling may be minor, or the area could double or triple in area. In addition to its appearance, the swollen area might be uncomfortable or hurt considerably. Depending on the cause, the skin may be wrinkled or stretched tight. Heaviness in the leg, cramping, warm skin, and varicose veins—any of these symptoms may accompany the swelling.

RELATED: What causes swollen legs from the knee down? Related conditions and treatments

Key takeaways:

  • Swelling in only one leg is a common symptom that may be caused by a blood clot, localized injury, vein problems, or fluid retention (edema). Other possible causes include sitting too long, severe infections, tumors, muscle tissue swelling, abnormal fat buildup, and medication side effects.

  • Typically, swelling in only one leg requires immediate medical attention.

  • Swelling in only one leg generally requires treatment. It may or may not resolve with treatment, depending on the cause.

  • Treatments of swelling in only one leg vary by cause. Read more about blood clots and deep vein thrombosis treatments to learn more.

  • Chronic swelling in only one leg can be managed with lifestyle changes, dietary changes, weight loss, compression garments, and leg massage.

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What causes swelling in only one leg?

Swelling in one leg can happen quickly or slowly develop into a chronic problem. The most common causes of acute swelling in one leg are:

  • Blood clots, including deep vein thrombosis (DVT)

  • Injury, typically a bone fracture or sprain

The most common causes of chronic swelling in one leg include:

  • Venous insufficiency: Venous insufficiency is a very common vascular disease in which the veins in the leg are not capable of returning all the blood in the leg to the chest. This may happen in one leg if that leg was involved in a trauma in the past. This is because the trauma can harm the veins and decrease their ability to drain the blood from the leg back to the heart. As a result, blood pools in the leg veins, causing varicose veins, and fluid leaks out, causing swelling. Venous insufficiency can affect one or both legs. 

  • Lymphedema: Lymphedema is a less common reason for swelling in one leg. This is due to a buildup of tissue fluids, primarily in the legs, because the fluid drainage system, the lymphatic system, is blocked. This often happens in just one leg but could happen in both.

Other causes of swelling in only one leg include:

  • Cellulitis of the leg: Cellulitis is a common bacterial skin infection that often only affects one leg. Symptoms include swelling, pain, redness, tenderness, blisters, and warmth.

  • Other infections of the connective tissues or joints: Two serious bacterial infections—necrotizing fasciitis and joint sepsis— produce swelling in one leg with severe pain and/or fever. 

  • After-effects of deep vein thrombosis: After a bout of DVT, 20% to 50% of people who recover will have long-term problems with the veins in that legs, a condition called post-thrombotic syndrome (PTS). Symptoms include chronic swelling, pain, and a sense of leg heaviness. 

  • Lipedema: The word “lipedema” means “fat swelling.” It’s an abnormal fat buildup in the lower extremities that doesn’t improve with weight loss. It usually affects both legs but can affect just one leg in exceptional cases.

  • Gravity: Sitting for long periods of time can cause fluid buildup in the dependent extremities (legs). Swelling usually involves both legs, but in uncommon cases, only one leg may be involved. 

  • Compartment syndrome: Compartment syndrome is a severe medical condition that involves pressure buildup within a leg muscle, usually the calf muscle. This usually occurs when exercising because excercise forces blood into the muscle. Besides swelling, people with this problem will have severe and even unbearable pain.

  • Some types of cancer

Certain medications can cause swelling in one or both legs including:

Should I be worried about swelling in only one leg?

Swollen legs are a cause for concern. If both legs start swelling, the cause may not be serious, like medication side effects, but it could be something to worry about, like congestive heart failure, kidney disease, and kidney failure. 

If only one leg swells, then see a healthcare provider. If a leg rapidly swells—within a few days or less—seek emergency medical treatment, particularly if accompanied by pain. Rapid onset of swelling in one leg is often due to a serious condition like a blood clot or cellulitis. An untreated blood clot in the leg can break loose and block arteries to the lungs, a life-threatening condition called pulmonary embolism. The second most common cause of sudden swelling in one leg is an injury such as a bone break, sprain, or muscle damage. These, too, can have potentially serious complications and should be treated as soon as possible.

How is the cause of swelling in only one leg diagnosed?

Diagnosing the cause of sudden swelling in one leg is based on symptoms, a medical history, and a physical exam of the leg. If a blood clot is suspected, the clinician will order an urgent ultrasound of the leg’s blood vessels (vascular ultrasound). Further testing for a blood clot may involve blood tests or a venogram using contrast dye. If there is a possibility of injury, X-rays can identify the injury or assess its severity. If cellulitis or other infections are thought to be the cause, blood tests or blood cultures may be used.

To diagnose chronic swelling of one leg, tests may not be necessary. A history and careful physical examination are usually enough to diagnose many causes of chronic swelling. If clinicians believe the swelling is due to venous insufficiency, they will need a vascular ultrasound of the leg.

Is swelling in only one leg contagious? 

Swelling in one leg is not contagious. It can sometimes be caused by serious infections such as cellulitis, necrotizing fasciitis, or septic arthritis. None of these infections are contagious.

How long does swelling in only one leg last?

Swelling in only one leg will last for as long as there’s an underlying condition causing it. Acute conditions such as blood clots, injuries, muscle swelling, and infections are treatable, and the swelling should recede in the days or weeks following successful treatment. Lymphedema and other conditions are typically chronic and lifelong. They are not curable, but people can manage leg swelling with lifestyle changes, dietary changes, compression garments, circulation pumps, and other conservative treatments.

How to stop swelling in only one leg

Leg swelling usually requires treatment. Treatment options for some of the most common causes of swelling in only one leg include:

  • Blood clots and DVT are treated with blood thinners and drugs that break up blood clots called thrombolytics. People may be asked to wear devices like compression stockings to improve blood flow. More serious cases may require surgery.

  • Chronic venous insufficiency can’t be cured but can be managed with leg elevation, exercise, weight loss, and compression stockings. In certain cases, a surgeon who specializes in vascular diseases will perform a saphenous vein ablation. This procedure closes off a major vein in the leg, allowing collateral veins to carry blood back to the heart. Venous insufficiency can cause skin sores. These ulcers may benefit from compression bandages, wound care, or surgery in the worst cases. 

  • Lymphedema can’t be cured, but symptoms are reduced with massage therapies, compression, circulation pumps, exercise, and surgery. Over-the-counter pain relievers can help with leg pain. Antibiotics are needed for any infections. 

For other health conditions that cause swelling in only one leg, clinicians will address them in a variety of ways:

  • Leg swelling due to excessive sitting can be addressed by lifestyle changes, including physical activity and weight loss.

  • Leg swelling due to cellulitis is treated with antibiotics.

  • Septic arthritis is treated with antibiotics, draining excess fluid from the affected joint.

  • Necrotizing fasciitis is usually treated in intensive care with surgery and antibiotics.

  • Compartment syndrome is a medical emergency requiring immediate surgery.

  • Lipedema is difficult to treat but can be slowed with a carbohydrate-reduced diet and exercise. Liposuction is an option.

RELATED: What causes edema? Diagnosis, prevention, and treatment

Living with swelling in only one leg 

Rapid swelling of only one leg requires immediate treatment. It’s not usually a lifelong or chronic condition, so the swelling and other symptoms should improve after treatment. However, gradual and persistent swelling in only one leg is different. Some health conditions that cause swelling in only one leg do not get better, but that doesn’t mean that the swelling and other symptoms like leg pain can’t be controlled through a few daily practices:

  • Lose weight and maintain a healthy weight

  • Eat healthy foods

  • Consider adopting an anti-inflammatory diet

  • Reduce salt intake. Less than 2 grams a day is best.

  • Move around as much as possible

  • Exercise

  • Try to build leg muscle strength

  • Elevate the swollen leg above the heart to help it drain

  • Wear compression garments. Put them on before your feet hit the floor in the morning.

  • Consider investing in a leg circulation pump that helps to improve blood flow in the circulatory system

  • Learn and practice lymphatic drainage massage for your legs

  • Learn and practice deep-tissue massage

  • Consider learning and doing lymphatic yoga

  • Don’t wear tight clothing or shoes

RELATED: 12 ways to reduce swelling

Most importantly, get immediate medical help if your legs swell rapidly

Swelling of the feet, ankles, lower legs, or legs is an important symptom whether it happens gradually or suddenly. Don’t ignore it. Talk to a doctor or other healthcare professional. This is especially true if only one or both legs swell rapidly. Rapid swelling in one leg is a bad sign, so immediate medical care is needed. It’s even more urgent if there are other symptoms like pain, tenderness, leg cramping, or warmth in one area. 

What’s next? Additional resources for people with swelling in only one leg

Test and diagnostics

Treatments

Scientific studies and clinical trials

Medically reviewed by Leslie Greenberg, MD
Board-Certified Family Physician

Leslie Greenberg, MD, is a board-certified practicing family physician with more than 25 years of doctoring experience. She was a psychology major at Northwestern University near Chicago, then graduated with an MD from the University of Nevada School of Medicine. She completed her family medicine residency at St. Joseph Hospital in Wichita, Kansas. She has trained more than 350 family medicine resident-physicians, been in private practice, and delivered babies for 22 years.

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