Swollen ankles happen when fluid builds up in the tissues around your ankle joint, a condition called edema. It can be as harmless as sitting too long on a flight or as serious as a sign of heart, kidney, or liver problems. The cause usually comes down to one question: is the swelling in one ankle or both?
Why Fluid Pools in Your Ankles
Your body constantly moves fluid between your bloodstream and surrounding tissues. Tiny blood vessels called capillaries push fluid out on the arterial side and pull it back in on the venous side, while your lymphatic system drains whatever is left over. Swelling happens when something tips this balance: pressure inside the capillaries gets too high, the vessel walls become too leaky, or the lymphatic system can’t keep up.
Gravity makes your ankles the first place this shows up. Blood has to travel the longest distance from your feet back to your heart, working against gravity the entire way. Veins in your legs have one-way valves that help push blood upward, but when those valves weaken, or when your heart isn’t pumping strongly enough, fluid has nowhere to go but into the surrounding tissue. Your kidneys also play a role. If they retain too much sodium and water, the extra volume raises pressure throughout your blood vessels, and the effect is most visible at the lowest point of your body.
Both Ankles Swollen: Common Causes
When swelling appears in both legs, it usually points to something affecting your whole body rather than a local problem in one leg.
Prolonged sitting or standing. Staying in one position for hours, whether at a desk or on your feet, lets gravity pull fluid downward. This is the most common and least concerning cause. The swelling typically goes away after you elevate your legs or move around.
Heart failure. When the heart can’t pump blood efficiently, blood backs up in the veins of the legs, ankles, and feet. The swelling tends to worsen throughout the day and may be accompanied by shortness of breath, especially when lying flat.
Kidney disease. Damaged kidneys struggle to filter sodium and water properly, causing fluid to accumulate. Kidney-related swelling often shows up in both the legs and around the eyes.
Liver disease. Cirrhosis can cause fluid buildup in the abdomen and legs. The liver produces a key blood protein that helps keep fluid inside your blood vessels; when the liver is damaged, levels of this protein drop and fluid leaks into tissues more easily.
Medications. Several common drug classes cause ankle swelling as a side effect. Blood pressure medications known as calcium channel blockers are among the most frequent culprits. Pain relievers like ibuprofen and naproxen cause the kidneys to hold onto sodium and water. Nerve pain medications such as gabapentin and pregabalin can do the same through a different mechanism. Other medications linked to swelling include certain diabetes drugs, steroids, some antipsychotics, and dopamine-related medications used for Parkinson’s disease. If your swelling started shortly after beginning a new prescription, that connection is worth exploring with your prescriber.
High sodium intake. Eating a lot of salt causes your body to retain water. Research on heart failure patients found that those consuming more than 3 grams of sodium per day had 2.5 times the risk of rehospitalization compared to those eating less. Even without heart failure, excess sodium contributes to fluid retention that shows up first in the ankles.
One Ankle Swollen: What’s Different
Swelling in just one leg raises a different set of concerns. The most important to rule out is a deep vein thrombosis, or blood clot. A DVT forms in a deep vein, usually in the calf or thigh, and blocks normal blood flow. Along with swelling, you may notice pain or cramping that starts in the calf, skin that looks red or purple, and warmth over the affected area.
DVT is dangerous not because of the leg swelling itself but because the clot can break free and travel to the lungs. This is called a pulmonary embolism, and it’s a medical emergency. Warning signs include sudden shortness of breath, chest pain that gets worse with deep breaths or coughing, a rapid pulse, dizziness or fainting, and coughing up blood. If you have swelling in one leg along with any of these symptoms, call emergency services immediately.
Other causes of one-sided swelling include an ankle sprain, infection, or a localized problem with the lymphatic system. An injury is usually obvious from the context, but unexplained swelling in a single leg always warrants medical evaluation.
Chronic Venous Insufficiency
If your ankles swell regularly, especially toward the end of the day or after long periods of standing, the valves in your leg veins may not be closing properly. This condition, chronic venous insufficiency, allows blood to flow backward and pool in the lower legs instead of returning to the heart. Over time, the increased pressure can burst tiny capillaries near the skin surface, giving the skin a reddish-brown discoloration.
Left untreated, the condition progresses. Severe cases lead to scar tissue forming in the lower leg, making the calf feel hard and swollen. The skin becomes fragile and vulnerable to open sores called venous ulcers that heal slowly. The progression is gradual, so people often dismiss early swelling as normal tiredness in their legs.
Pregnancy-Related Swelling
Some ankle swelling during pregnancy is normal, particularly in the third trimester, as the growing uterus puts pressure on veins that return blood from the legs. However, sudden swelling in the face, hands, or feet can be a warning sign of preeclampsia, a serious condition involving high blood pressure. Preeclampsia requires prompt medical attention because it can affect both the mother and baby.
How to Check the Severity
You can get a rough sense of how much fluid has accumulated by pressing a finger firmly into the swollen area, just above the ankle bone, for about 20 seconds. If your finger leaves a visible dent that stays for a few seconds, that’s called pitting edema. Doctors grade it on a scale based on how deep the indent goes: a shallow dent under 4 millimeters is mild (grade 1), while a deep dent of 8 millimeters or more is severe (grade 4). Deeper pitting and longer rebound times suggest more significant fluid retention that likely needs medical investigation.
Reducing Ankle Swelling
For swelling caused by gravity and inactivity rather than an underlying disease, several strategies help. Elevating your legs above heart level for 15 to 20 minutes lets gravity work in your favor, draining fluid back toward your core. Moving regularly, even just flexing your ankles or taking a short walk every hour, activates the calf muscles that act as a pump for your veins.
Compression stockings apply graduated pressure that helps push fluid upward. For mild occupational swelling from sitting or standing all day, stockings in the 15 to 20 mmHg range are effective. Research shows that even light compression of 10 to 15 mmHg can prevent occupational edema, with the effects visible after just two days of use. People who sit for most of their workday may benefit from a slightly higher pressure range of 20 to 30 mmHg. Calf-length stockings are sufficient for most people.
Cutting back on sodium makes a meaningful difference, particularly if your current intake is high. Most of the sodium in a typical diet comes from processed and restaurant foods rather than the salt shaker, so reading labels and cooking more meals at home are practical starting points.
When Swollen Ankles Signal an Emergency
Most ankle swelling develops gradually and isn’t immediately dangerous, but certain combinations of symptoms require urgent care. Seek emergency help if swelling comes with chest pain, difficulty breathing, shortness of breath when lying down, dizziness or fainting, or coughing up blood. These can indicate a blood clot in the lungs or a serious heart condition. Swelling that appears suddenly in one leg, particularly with pain, warmth, or skin discoloration, also needs same-day evaluation to rule out a DVT.