Ankle edema happens when fluid leaks out of your blood vessels and pools in the tissue around your ankles and feet. The causes range from something as simple as standing too long to serious conditions involving your heart, kidneys, or liver. Whether one ankle is swollen or both can tell you a lot about what’s going on.
How Fluid Ends Up in Your Ankles
Your blood vessels constantly balance two opposing forces. Pressure inside the vessel pushes fluid out through the vessel walls, while proteins in your blood (mainly albumin) pull fluid back in. When that balance tips in either direction, fluid escapes into surrounding tissue faster than your lymphatic system can drain it away. Gravity does the rest, pulling that extra fluid down to the lowest point in your body: your ankles and feet.
This means ankle swelling can result from three basic problems. Either too much pressure is pushing fluid out, too little protein is pulling it back in, or the drainage system itself is blocked or damaged. Nearly every specific cause of ankle edema traces back to one of these three mechanisms.
One Ankle vs. Both Ankles
This distinction matters more than most people realize. Swelling in just one ankle usually points to a local problem: a blood clot, an injury, an infection, or lymphatic damage. The left leg is affected more often in lymphatic conditions, with about 75% of cases being one-sided. Swelling in both ankles typically signals something systemic, like heart failure, kidney disease, liver disease, venous insufficiency, or a medication side effect.
A blood clot in a deep vein (DVT) is one of the more urgent causes of one-sided swelling. Along with the swelling, you may notice pain or tenderness, warmth, and redness or discoloration in the affected leg. If a clot breaks loose and travels to the lungs, it can cause sudden shortness of breath, chest pain, coughing, or fainting. That combination is a medical emergency.
Cellulitis, a bacterial skin infection, also causes swelling in one leg. The skin typically looks red, feels warm, and may be painful to touch. Keeping skin and nails clean and well-maintained helps prevent these infections, especially if you already have circulation problems.
Chronic Venous Insufficiency
This is one of the most common causes of persistent ankle swelling, particularly in people who spend long hours on their feet. Your leg veins have one-way valves that push blood upward toward the heart. When those valves fail, blood pools in the lower legs, and pressure builds in the small vessels near your ankles.
Valve failure happens several ways. Most often, naturally thin vein walls stretch under normal pressure until the valve flaps can no longer meet in the middle. Direct injury, blood clots, or inflammation can also damage valves. Whatever the cause, the result is the same: an unbroken column of blood sits in the vein, and pressure stays high even when you’re walking.
That high pressure triggers a chain reaction. It slows blood flow in the tiniest vessels, trapping white blood cells that release inflammatory chemicals. These chemicals damage vessel walls, letting proteins leak into surrounding tissue and forming a fibrous cuff around the vessels. Over time, oxygen delivery drops, and you may see skin changes like darkening, thickening, or even open sores near the ankles.
Heart Failure
When the heart can’t pump blood efficiently, two things happen that both lead to ankle swelling. First, blood backs up in the veins, raising pressure in the vessels of your legs. Second, reduced blood flow to the kidneys triggers a cascade of hormonal signals that tell the body to hold on to salt and water.
These hormonal systems were designed to help during short-term crises like dehydration or blood loss. In heart failure, they stay activated chronically. The kidneys keep retaining sodium and water even though the body already has too much fluid. This creates a cycle: more fluid means more work for an already struggling heart, which means even less blood reaching the kidneys, which means even more fluid retention. The extra fluid shows up as swelling in the ankles and feet, shortness of breath, and fatigue.
Kidney and Liver Disease
Your kidneys and liver both play central roles in keeping fluid where it belongs, and problems with either organ can send fluid into your ankles.
In kidney disease, particularly nephrotic syndrome, the tiny filters in the kidneys become damaged and start leaking albumin into the urine. Albumin is the main protein responsible for pulling fluid back into your blood vessels. As albumin levels drop, fluid escapes into tissue throughout the body, but it’s often most noticeable around the eyes, ankles, and feet.
Liver disease causes edema through a similar protein problem. A damaged liver can’t produce enough albumin, so the same drop in fluid-pulling pressure occurs. Advanced liver disease also raises pressure in the veins draining the gut and lower body, adding a second mechanism that pushes fluid out of the vessels. The result can be swelling in both the abdomen and the lower legs.
Medications That Cause Ankle Swelling
Certain blood pressure medications are a surprisingly common cause. Calcium channel blockers, a widely prescribed class that relaxes blood vessel walls, dilate the small arteries in your legs more than the veins. This mismatch increases pressure in the tiny vessels near your ankles and pushes fluid out.
The effect is strongly dose-dependent. At starting doses of common options like amlodipine, only about 5% of patients notice ankle swelling. At very high doses, that number can exceed 80%. Combining these medications with another type of blood pressure drug (an ACE inhibitor or ARB) reduces the swelling by about 38% and cuts the number of people who need to stop the medication due to edema by 62%.
Other medications that can cause ankle swelling include certain diabetes drugs, anti-inflammatory painkillers, steroids, and some hormonal therapies. If you notice new ankle swelling after starting a medication, it’s worth bringing up with whoever prescribed it.
Pregnancy
Some degree of ankle swelling is normal during pregnancy, especially in the third trimester. Your body retains more fluid than usual, and the growing uterus presses on the large veins that return blood from your legs. Both effects make it harder for fluid to leave the lower extremities.
What isn’t normal is sudden or rapidly worsening swelling, particularly in the face or hands. This pattern can signal preeclampsia, a condition involving dangerously high blood pressure that needs prompt medical attention. Gradual, mild swelling in both ankles that gets worse during the day and improves overnight is generally part of a normal pregnancy.
Thyroid Disease
Severe, advanced hypothyroidism (an underactive thyroid) can cause a distinctive type of swelling called myxedema. Unlike most forms of edema, this swelling involves a buildup of sugary molecules in the skin rather than just water. It typically appears alongside other signs of low thyroid function: a slow heart rate, constipation, weight gain, and fatigue.
How Pitting Edema Is Graded
When a provider presses a finger into swollen tissue and it leaves a temporary dent, that’s called pitting edema. The depth of the dent and how long it takes to bounce back indicate severity:
- Grade 1: A 2 mm dent that rebounds immediately
- Grade 2: A 3 to 4 mm dent that rebounds in under 15 seconds
- Grade 3: A 5 to 6 mm dent that takes 15 to 60 seconds to rebound
- Grade 4: An 8 mm dent that takes two to three minutes to rebound
Not all swelling pits when pressed. Lymphedema and myxedema from thyroid disease often feel firmer and don’t leave a dent. That distinction helps identify the underlying cause.
Patterns That Point to the Cause
A few practical observations can help narrow down what’s behind your ankle swelling. Swelling that appears by evening and resolves overnight suggests a positional or venous cause. Swelling that persists through the morning is more common with heart, kidney, or liver problems. Swelling that gets worse with heat, prolonged sitting, or salty meals often reflects mild venous insufficiency or fluid retention rather than organ disease.
Skin changes around the ankles offer clues too. Brownish discoloration and thickened skin suggest long-standing venous insufficiency. Red, warm, tender skin points toward infection or a clot. Taut, shiny skin with rapid onset could reflect worsening heart or kidney function. Pain that’s out of proportion to the visible swelling, especially in one leg, raises concern for a deep vein clot.