10/01/2026
What Can Cause Leg Swelling?
Leg swelling, also called lower-extremity edema, happens when excess fluid builds up in the tissues of the leg. It can occur in one leg or both, and the cause can vary quite a bit depending on how the swelling develops and what other symptoms are present.
When swelling occurs in one leg
Swelling that affects just one leg can have several possible causes, including:
* Deep vein thrombosis (DVT) — a blood clot in a deep vein that can cause sudden swelling, pain, warmth, or redness.
* Cellulitis — a bacterial infection of the skin and underlying tissues that can cause redness, warmth, tenderness, and swelling.
* An injury or fracture — trauma can lead to localized inflammation and fluid buildup.
* Muscle or ligament injuries — strains, sprains, and other soft-tissue injuries may cause swelling around the affected area.
* A ruptured Baker’s cyst — fluid from behind the knee can leak into the lower leg and create swelling.
* Lymphatic blockage or dysfunction — when lymph isn’t moving properly, fluid can accumulate in the tissues.
* Venous obstruction or compression — problems with blood returning through the veins can contribute to swelling.
* Superficial thrombophlebitis — inflammation and clotting in a superficial vein can cause localized swelling, tenderness, redness, and warmth.
When swelling occurs in both legs
Swelling in both legs can sometimes point toward an underlying systemic or circulatory issue. Possible causes include:
* Chronic venous insufficiency — when the veins have difficulty returning blood back toward the heart. Swelling may become more noticeable after standing or sitting for long periods.
* Heart failure — can lead to fluid accumulation in both legs and may occur along with shortness of breath or reduced exercise tolerance.
* Kidney disease — impaired kidney function can cause the body to retain excess fluid.
* Liver disease — changes in fluid balance and low protein levels can contribute to edema.
* Hypothyroidism
* Low protein or albumin levels
* Long periods of sitting or standing
* Pregnancy
* Obesity
* Certain medications
Medications can also contribute to swelling
Some medications are known to cause or worsen leg edema. Examples include:
* Amlodipine and other calcium-channel blockers
* NSAIDs, such as ibuprofen
* Corticosteroids
* Certain diabetes medications, including pioglitazone
* Some hormone-based medications
When leg swelling needs immediate attention
Not all swelling is the same, and some situations should be evaluated promptly by a medical professional.
Seek urgent medical attention if swelling:
* Appears suddenly, particularly in one leg
* Is accompanied by chest pain or sudden shortness of breath
* Comes with significant pain, redness, or warmth
* Is accompanied by fainting or coughing up blood
Looking at the bigger picture
When evaluating swelling, it’s important to look beyond the swelling itself. Is it affecting one leg or both? Did it come on suddenly or develop gradually? Are there changes in the skin, pain, warmth, redness, or other symptoms?
Those details can help point toward whether the swelling may be related to the venous system, lymphatic system, an injury, medication, or an underlying medical condition.
As an MLD therapist, I don’t diagnose the cause of swelling. My role is to recognize changes that may warrant medical evaluation and, when appropriate and medically cleared, support healthy lymphatic fluid movement through Manual Lymphatic Drainage.
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