Swollen Ankles and Legs: Causes and When to Worry

Why do ankles and feet swell?

Swelling in the lower legs and ankles occurs when fluid accumulates in the spaces between cells — a process called edema. This happens when:

• Pressure in the veins rises above what the vessel walls can contain, forcing fluid into surrounding tissue 1Ref 1Eberhardt RT, Raffetto JD (2014).Chronic Venous Insufficiency.Chronic venous insufficiency as a leading cause of bilateral lower-extremity edema; pathophysiology of venous hypertension; management with graduated compression and leg elevation
• Blood protein levels fall, reducing the osmotic pull that keeps fluid inside blood vessels
• The lymphatic system cannot drain excess fluid efficiently
• The kidneys retain too much salt and water

Gravity plays a role: when we are upright all day, fluid tends to pool in the lowest point — the feet and ankles. This is why swelling is often worse in the evening and better in the morning after a night lying flat.

What are the most common causes?

Prolonged sitting or standing. Desk workers, travelers on long flights, and people in jobs that require standing all day commonly develop mild ankle swelling by the end of the day. This is generally harmless and resolves with movement and leg elevation.

Chronic venous insufficiency. Faulty vein valves allow blood to pool in the lower legs, raising venous pressure and causing persistent edema 1Ref 1Eberhardt RT, Raffetto JD (2014).Chronic Venous Insufficiency.Chronic venous insufficiency as a leading cause of bilateral lower-extremity edema; pathophysiology of venous hypertension; management with graduated compression and leg elevation. This is one of the most common causes of bilateral leg swelling in adults and often comes with skin changes over time — discoloration, thickening, or even ulcers in severe cases.

Medications. Calcium channel blockers (a common class of blood pressure medication), certain diabetes drugs, NSAIDs, and corticosteroids can all cause lower-leg swelling. This is one of the first things a clinician will review when evaluating new edema.

Heart failure. When the heart cannot pump efficiently, pressure builds up in the venous system, forcing fluid into the tissue — particularly in the legs and ankles when sitting or standing 2Ref 2Heidenreich PA, Bozkurt B, Aguilar D, et al. (2022).2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure.Heart failure as a major cause of bilateral lower-extremity edema; management including diuretics, sodium restriction, and symptom recognition such as orthopnea. Accompanying symptoms often include shortness of breath, fatigue, and reduced exercise capacity.

Kidney disease. Diseased kidneys may retain excess salt and water or fail to maintain blood protein levels, both of which cause edema.

Liver disease. The liver produces albumin, a protein that keeps fluid in the bloodstream. Significant liver disease lowers albumin, allowing fluid to leak into surrounding tissues.

Deep vein thrombosis (DVT). A blood clot in a deep leg vein causes one-sided swelling, often with pain, warmth, and redness 3Ref 3Marcus GM (2020).Evaluation and Management of Premature Ventricular Complexes.Clinical evaluation and diagnostic workup for unilateral leg swelling suspicious for deep vein thrombosis. This is a medical concern because the clot can travel to the lungs.

Does the pattern of swelling give clues?

Both legs, symmetric, worse in the evening: Most consistent with venous insufficiency, prolonged dependency, medication effect, or a systemic cause like heart or kidney disease 1Ref 1Eberhardt RT, Raffetto JD (2014).Chronic Venous Insufficiency.Chronic venous insufficiency as a leading cause of bilateral lower-extremity edema; pathophysiology of venous hypertension; management with graduated compression and leg elevation2Ref 2Heidenreich PA, Bozkurt B, Aguilar D, et al. (2022).2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure.Heart failure as a major cause of bilateral lower-extremity edema; management including diuretics, sodium restriction, and symptom recognition such as orthopnea.

One leg only, with pain or redness: Raises concern for DVT or local infection. Needs prompt evaluation 3Ref 3Marcus GM (2020).Evaluation and Management of Premature Ventricular Complexes.Clinical evaluation and diagnostic workup for unilateral leg swelling suspicious for deep vein thrombosis.

Swelling that is worse in the morning (or does not improve overnight): More concerning for systemic disease rather than simple positional causes.

Swelling with shortness of breath when lying flat (orthopnea): Strongly suggests heart failure and warrants timely evaluation 2Ref 2Heidenreich PA, Bozkurt B, Aguilar D, et al. (2022).2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure.Heart failure as a major cause of bilateral lower-extremity edema; management including diuretics, sodium restriction, and symptom recognition such as orthopnea.

Swelling with facial puffiness or frothy urine: Points toward kidney disease with protein loss.

When should I see a clinician about swollen legs?

Mild, symmetric ankle swelling that is worse at day's end, improves with elevation, and has been present and stable for years — especially in someone with a known cause — does not usually require urgent evaluation.

You should seek evaluation when: - Swelling is new or has worsened recently - Only one leg is swollen - Swelling comes with shortness of breath, reduced exercise tolerance, or difficulty breathing when lying down - You have pain in the calf - Skin over the swollen area is red, hot, or breaking down

What helps with swollen ankles and legs?

Self-care for mild, positional swelling:

• Leg elevation. Raising legs above heart level for 20–30 minutes several times a day helps fluid return to circulation.
• Graduated compression stockings. A well-fitted pair of compression socks reduces venous pooling and is particularly helpful for venous insufficiency 1Ref 1Eberhardt RT, Raffetto JD (2014).Chronic Venous Insufficiency.Chronic venous insufficiency as a leading cause of bilateral lower-extremity edema; pathophysiology of venous hypertension; management with graduated compression and leg elevation.
• Movement. Walking and calf exercises pump blood upward through the venous system.
• Reducing sodium. Dietary salt promotes fluid retention throughout the body.

For swelling caused by an underlying condition, treatment targets the cause — diuretics for heart failure 2Ref 2Heidenreich PA, Bozkurt B, Aguilar D, et al. (2022).2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure.Heart failure as a major cause of bilateral lower-extremity edema; management including diuretics, sodium restriction, and symptom recognition such as orthopnea, management of venous insufficiency 1Ref 1Eberhardt RT, Raffetto JD (2014).Chronic Venous Insufficiency.Chronic venous insufficiency as a leading cause of bilateral lower-extremity edema; pathophysiology of venous hypertension; management with graduated compression and leg elevation, or adjusting medications.

A Gale primary care clinician can assess whether your swelling needs investigation, order relevant tests such as an echocardiogram or kidney function panel, review your medications, and refer you if a specialist is needed.