Why does deep vein thrombosis cause swollen ankles?

Deep veins carry blood back toward the heart. If a clot forms in a leg vein, pressure can rise behind the blockage and fluid can move into tissues, making part of the leg, calf, ankle, or foot look or feel swollen. Swollen Ankles is a common presentation of Deep Vein Thrombosis. The swelling may occur with pain, warmth, tenderness, or skin redness, although symptoms vary.

Many conditions besides a clot can cause ankle swelling, including injury, vein problems, medicines, and heart, kidney, or liver conditions. A new one-sided swollen leg needs medical assessment rather than self-diagnosis.

Arrange urgent medical assessment for new unexplained swelling in one leg, especially if it is painful, warm, or tender. Do not massage the area. A clinician may examine the leg and arrange imaging or blood tests to check for a clot. If deep vein thrombosis is confirmed, treatment aims to prevent the clot from enlarging or travelling.

Call emergency services immediately for sudden shortness of breath, chest pain that worsens with breathing, coughing up blood, fainting, or a rapid heartbeat with leg swelling. These can signal a clot affecting the lungs and require emergency care.

Ask what may be causing the swelling, whether a scan is needed, and whether recent travel, surgery, immobility, pregnancy, hormone treatment, or previous clots affect your assessment. Also ask which symptoms should prompt emergency help.