Leg swelling and pain: possible causes and when to seek medical advice

Leg swelling occurs when fluid builds up in the tissues. Pain may develop along with the swelling or independently of it. Symptoms may affect one or both legs and may develop gradually or suddenly. The appearance of the leg alone is not enough to identify the cause.

Common causes

• Prolonged standing or sitting, venous insufficiency and varicose veins.
• Sprains, bruises and other muscle or joint injuries.
• Inflammatory or infectious conditions of the skin and soft tissues.
• Deep vein thrombosis, particularly when one leg swells suddenly.
• Heart, kidney or liver disease, certain medicines and other systemic causes of swelling.

Swelling in both legs toward the evening does not necessarily mean varicose veins. Likewise, calf pain is not always caused by a venous problem. The speed of onset, accompanying symptoms, medications and medical history all matter when making a diagnosis.

When a routine appointment may be appropriate

If swelling recurs, worsens toward the end of the day or is accompanied by heaviness, visible enlarged veins or skin changes, discuss it with your family doctor or an appropriate specialist. Do not wait for a routine appointment if swelling in one leg is unexplained.

It is important to consider how long the swelling has been present and what other symptoms occur alongside it.

• Increased size of the lower leg, foot or ankle.
• Heaviness, a feeling of tightness, aching or throbbing pain.
• Redness, warmth or tenderness of the skin.
• Visible twisted veins or darker skin near the ankles.
• Pain when moving, after an injury or when putting weight on the leg.

Symptoms may overlap between different conditions. Even with a previous diagnosis of varicose veins, new and sudden swelling should not automatically be attributed to them.

The doctor will ask when and how the pain began, whether there was an injury or a prolonged period of immobility, which medicines you take and whether you have had blood clots before. During the examination, both legs, skin color, temperature, swelling, pulses and other findings are assessed.

If venous thrombosis is suspected, urgent assessment based on clinical criteria is needed. The clinician may order a D-dimer blood test and/or compression ultrasound of the veins when indicated. Duplex ultrasound is used to assess chronic venous symptoms. Other tests depend on the most likely cause.

Treatment for leg swelling and pain depends on the diagnosis: the same advice is not appropriate for injury, infection, venous insufficiency and thrombosis. Once the cause is known, changes in activity, treatment of the underlying condition or specialist therapy may be needed.

For gradual, uncomplicated swelling, regular walking, breaks from prolonged sitting and resting with the legs elevated may help. But if one leg suddenly becomes painful and swollen, do not start compression, massage or blood-thinning medicines on your own instead of seeking assessment.