Ankle swelling happens when fluid builds up in the tissues around your ankle joint, and the causes range from something as simple as standing too long to serious conditions involving the heart, kidneys, or veins. One of the most useful clues is whether the swelling affects one ankle or both, since that distinction points toward very different underlying problems.
Why One Ankle vs. Both Ankles Matters
Swelling in just one ankle typically signals a local problem: a blood clot, an injury, an infection, or a blockage in the veins or lymphatic system on that side. Swelling that develops in one leg over less than 72 hours is more characteristic of deep vein thrombosis (DVT), cellulitis, or a ruptured cyst behind the knee. If the swollen ankle is also tender to the touch, DVT and certain pain syndromes become more likely.
When both ankles swell, the cause is usually systemic, meaning something affecting your whole body. Heart failure, kidney disease, liver disease, and severe malnutrition can all produce bilateral swelling. Certain medications do too. This pattern reflects a body-wide shift in how fluid is managed rather than a problem at one specific site.
Heart Failure and Fluid Backup
Congestive heart failure is one of the most common serious causes of ankle swelling. When the heart can no longer pump blood efficiently, blood lingers in the veins. That lingering blood raises pressure inside the vessels, which forces fluid out into surrounding tissues. Because gravity pulls blood downward, this fluid tends to collect in the ankles and feet first, especially if you’ve been standing or sitting for hours.
The swelling from heart failure is usually bilateral, worsens throughout the day, and improves overnight when your legs are elevated. You might also notice shortness of breath, fatigue, or rapid weight gain from fluid retention. If pressing on the swollen area leaves a visible dent that slowly fills back in (called pitting edema), that’s consistent with the kind of fluid buildup heart failure produces.
Chronic Venous Insufficiency
About 1 in 20 adults has chronic venous insufficiency (CVI), a condition where the one-way valves inside leg veins stop working properly. Normally those valves keep blood moving upward toward the heart against gravity. When a valve becomes damaged, blood flows backward and pools in the lower legs. The increased pressure pushes fluid into the tissues around the ankle.
CVI develops gradually. Early on you may notice your ankles swelling by the end of the day, then returning to normal overnight. Over time, the skin around the ankles can darken, become itchy, or develop open sores called venous ulcers. Risk factors include a history of blood clots, obesity, pregnancy, prolonged standing, and age. Unlike DVT, which comes on suddenly, CVI is a slow-building problem that worsens over months or years.
Kidney and Liver Disease
Your kidneys and liver both play central roles in keeping fluid balanced. When the kidneys are damaged, they struggle to filter excess sodium and water, which accumulates in your tissues. Kidney disease also allows a protein called albumin to leak out of the blood and into the urine. Albumin normally acts like a sponge inside your blood vessels, holding fluid in. When albumin levels drop, fluid seeps into surrounding tissue more easily.
Liver disease, particularly cirrhosis, causes a similar problem. A damaged liver produces less albumin, and the resulting drop in blood protein lets fluid escape into the legs and abdomen. In both cases, the swelling is bilateral, develops gradually, and often appears alongside other symptoms like fatigue, changes in urination, or abdominal bloating.
Medications That Cause Ankle Swelling
A category of blood pressure medications called calcium channel blockers is one of the most common pharmaceutical causes of ankle swelling. These drugs relax blood vessels to lower blood pressure, but that relaxation also allows more fluid to leak into surrounding tissues. The incidence ranges from about 1% to 15% of patients on standard doses, but at high doses taken long-term, swelling can affect more than 80% of patients. Combining these medications with another type of blood pressure drug (an ACE inhibitor) roughly cuts the swelling rate in half.
Other medications linked to ankle swelling include certain diabetes drugs, steroids, hormone replacement therapy, and some antidepressants. If you notice swelling starting shortly after beginning a new medication, that timing is an important clue.
Pregnancy-Related Swelling
Ankle swelling during pregnancy is considered normal. The growing uterus puts pressure on the veins that return blood from the legs, and hormonal changes cause the body to retain more fluid. Most pregnant women experience at least some swelling in their feet and ankles, particularly in the third trimester.
The concern is when ankle swelling signals preeclampsia, a serious pregnancy complication. The key distinction: preeclampsia involves blood pressure of 140/90 mmHg or above, protein in the urine, and swelling that extends to the hands, arms, or face with greater-than-expected weight gain. A woman with mild preeclampsia may not notice symptoms at all. Severe preeclampsia pushes blood pressure to 160/110 or higher and can cause headaches, vision changes, reduced urine output, and abdominal pain. Normal pregnancy ankle swelling, by contrast, stays in the feet and lower legs and isn’t accompanied by elevated blood pressure.
Lymphedema
Your lymphatic system drains excess fluid from tissues and routes it back into circulation. When this system is damaged or blocked, fluid accumulates in the affected area. Lymphedema in the ankles and legs can result from cancer treatment (particularly surgery or radiation that removes or damages lymph nodes), infection, or, more rarely, a congenital problem with the lymphatic system.
Lymphedema has a distinctive feel and progression. Unlike the soft, pitting swelling of heart failure or venous insufficiency, lymphedema tends to make the skin thicker, harder, and more fibrotic over time. In severe cases, the skin can thicken so dramatically it resembles elephant skin. Lymph fluid may even leak through small breaks in the skin surface. Notably, lymphedema is generally painless to the touch, which distinguishes it from DVT, where the swollen area is typically tender. Recurring infections in the swollen limb are another hallmark.
Lifestyle and Positional Causes
Not all ankle swelling points to disease. Gravity alone can do it. Sitting for long stretches, especially during flights or desk work, allows fluid to pool in the lower legs. Standing all day has the same effect. Eating a high-sodium meal can cause temporary fluid retention that shows up most noticeably in the ankles. Hot weather dilates blood vessels and increases fluid leakage into tissues.
Injuries deserve mention too. A sprained or fractured ankle produces localized swelling from inflammation, and the cause is usually obvious from the pain and circumstances. Insect bites and minor infections near the ankle can cause swelling limited to the surrounding area.
Managing Mild Swelling at Home
For swelling caused by prolonged sitting, standing, or minor fluid retention, a few strategies help. Elevating your legs above heart level encourages fluid to drain back toward your core. Moving regularly, even short walks, activates the calf muscles that pump blood upward through the veins. Reducing sodium intake limits fluid retention.
Compression stockings apply graduated pressure that helps push fluid out of the ankle area. Mild compression (8 to 15 mmHg) works for tired, achy legs and minor swelling. For more severe conditions like significant varicose veins, venous ulcers, or pronounced edema, extra-firm compression (30 to 40 mmHg) is typically prescribed. Getting the right level matters, since too little compression won’t help and too much can restrict circulation.
When Ankle Swelling Needs Attention
Sudden swelling in one leg, especially with pain, warmth, or redness, is the pattern most concerning for a blood clot and warrants prompt evaluation. Bilateral swelling that comes on gradually and doesn’t resolve with elevation or rest could indicate a heart, kidney, or liver problem, particularly if you also have shortness of breath, fatigue, or changes in urination. Swelling during pregnancy that spreads to the hands or face, or comes with headaches and vision changes, needs immediate evaluation for preeclampsia. And any swelling that progressively worsens over weeks, produces skin changes, or causes recurring infections points toward chronic venous insufficiency or lymphedema that benefits from early treatment.