Ankle swelling happens when fluid accumulates in the tissue around your ankle joint, and the cause ranges from something as simple as sitting too long to something as serious as a blood clot or heart problem. Whether one ankle is swollen or both can tell you a lot about what’s going on. A single swollen ankle usually points to a local issue like an injury or infection, while both ankles swelling together often signals something systemic, like a problem with your heart, kidneys, or veins.
How Fluid Builds Up in Your Ankles
Your body constantly moves fluid between your bloodstream and the surrounding tissue. Small blood vessels called capillaries let fluid seep out to nourish cells, and your lymphatic system drains it back. Swelling occurs when more fluid leaks out of the capillaries than the lymphatic system can return. Gravity pulls that excess fluid downward, which is why your ankles and feet are usually the first place it shows up.
Several things can tip this balance. Increased pressure inside your veins pushes more fluid out. Low protein levels in your blood (from kidney or liver problems) reduce the pull that keeps fluid inside your vessels. Inflammation from an injury or infection makes capillary walls leakier. And if the lymphatic drainage pathways get blocked or damaged, fluid simply has nowhere to go.
Injuries and Infections
The most common reason for a single swollen ankle is an injury. Sprained ankles, fractures, and torn tendons all trigger an inflammatory response that floods the area with fluid. You’ll typically have pain, bruising, or difficulty bearing weight alongside the swelling. If you recently twisted your ankle or had any kind of impact, the swelling is almost certainly related.
Cellulitis, a bacterial skin infection, can also cause one ankle to swell rapidly. The skin over the area usually turns red, feels warm, and may be tender to the touch. This needs prompt treatment with antibiotics because it can spread quickly.
Venous Insufficiency and Blood Clots
Chronic venous insufficiency, where the veins in your legs struggle to push blood back up to your heart, is one of the most common causes of persistent ankle swelling. Over 25 million adults in the United States have varicose veins, and roughly 2.5 million experience more advanced venous insufficiency. The condition becomes more common with age: about 21% of men and 12% of women over 50 are affected. Weakened or damaged valves inside the veins allow blood to pool in the lower legs, forcing fluid into the surrounding tissue.
A more dangerous vein problem is deep vein thrombosis (DVT), a blood clot that forms in a deep leg vein. DVT typically affects one leg and causes swelling along with cramping or soreness that often starts in the calf, skin color changes (red or purple), and warmth over the affected area. DVT is a medical emergency because the clot can break loose and travel to your lungs, causing a pulmonary embolism. Seek emergency care if you develop sudden shortness of breath, chest pain that worsens when you breathe or cough, a rapid pulse, dizziness, fainting, or coughing up blood.
Heart, Kidney, and Liver Problems
When both ankles swell gradually over days or weeks, the cause may be an organ that isn’t working well. Each organ creates a distinct pattern.
In heart failure, one or both of the heart’s lower chambers stop pumping blood effectively. Blood backs up in the veins, raising pressure and pushing fluid into the legs, ankles, and feet. You may also notice swelling in the abdomen, shortness of breath (especially when lying flat), and fatigue. Fluid can build up in the lungs, making it harder to breathe.
Kidney disease prevents your body from properly filtering excess fluid and salt from the blood. The swelling tends to show up in the legs and also around the eyes, which is a distinguishing clue. A more specific form of kidney damage called nephrotic syndrome causes protein to leak out of the blood, reducing the force that holds fluid inside your vessels.
Liver scarring (cirrhosis) causes fluid to accumulate in the abdomen and legs. The abdominal swelling is often the more prominent symptom and can be the first sign that something is wrong with the liver.
Medications That Cause Swelling
Several common medications can trigger ankle swelling as a side effect. Over-the-counter pain relievers like ibuprofen and naproxen are frequent culprits, especially with regular use. Some blood pressure medications, diabetes drugs, and hormone therapies (including estrogen and testosterone) can also cause fluid retention. Chemotherapy is another known cause. If your ankle swelling started around the same time as a new prescription or an increase in dose, the medication may be responsible.
Lifestyle and Temporary Causes
Not every swollen ankle signals a medical problem. Sitting for long stretches, like on a long flight, keeps blood pooling in your lower legs. Standing all day has the same effect. Carrying extra body weight increases the pressure on your veins and makes it harder for fluid to circulate efficiently. Eating a high-sodium diet causes your body to hold onto water, and that extra fluid tends to settle in your ankles. Even tight clothing or stockings that compress the upper leg can slow venous return enough to cause puffiness below.
Ankle Swelling During Pregnancy
Mild ankle swelling is normal during pregnancy, especially in the third trimester. The growing uterus compresses veins in the pelvis, slowing blood flow from the legs, and increased blood volume adds to the fluid load. But sudden or severe swelling, particularly in the face and hands along with the ankles, can be a warning sign of preeclampsia. This condition involves new-onset high blood pressure (140/90 or higher) typically after 20 weeks of pregnancy. If rapid swelling is accompanied by headaches, vision changes, or upper abdominal pain, it requires immediate medical evaluation.
How to Check the Severity
You can get a rough sense of how significant your swelling is with a simple test: press your thumb firmly into the swollen area for a few seconds, then release. If it leaves an indentation, that’s called pitting edema, and the depth and rebound time indicate severity. A shallow 2-millimeter dent that springs back immediately is grade 1, the mildest form. A deeper pit of 3 to 4 millimeters that takes up to 15 seconds to refill is grade 2. Grade 3 leaves a 5 to 6 millimeter pit that takes up to a minute to rebound. Grade 4 creates an 8 millimeter pit that can take two to three minutes to fill back in. Grades 3 and 4 generally indicate more significant fluid retention that warrants medical attention.
Reducing Ankle Swelling at Home
For mild or lifestyle-related swelling, elevation is the simplest and most effective remedy. Lying down and propping your feet up on a pillow (about 10 centimeters, or 4 inches, above the level of your heart) is enough to help fluid drain back toward your core. Research on post-surgical ankle patients found that moderate elevation on a pillow worked just as well as higher elevation and was considerably more comfortable. Try to elevate for 20 to 30 minutes several times a day if you can.
Cutting back on sodium helps reduce fluid retention. The American Heart Association recommends staying under 1,500 milligrams of sodium per day for the general population. For context, a single teaspoon of table salt contains about 2,300 milligrams, and most processed and restaurant foods are loaded with it. Moving your ankles and calves regularly throughout the day, even simple ankle circles or calf raises, activates the muscle pump that pushes blood upward through your veins. Compression socks can also help if you’re on your feet or sitting for long periods.
If your swelling is persistent, worsening, affects only one leg, comes with pain or skin changes, or is accompanied by shortness of breath or chest discomfort, those patterns point to causes that need a proper diagnosis rather than home management.