Ankle swelling happens when fluid builds up in the tissues around your ankle joint. The causes range from something as simple as sitting too long on a flight to serious conditions like heart failure or blood clots. Understanding the pattern of your swelling, whether it affects one ankle or both, and what other symptoms come with it can help you figure out what’s behind it.
Prolonged Sitting and Standing
The most common and least worrisome cause is gravity. When you sit or stand in one position for hours, fluid naturally pools in the lowest parts of your body. This is called dependent edema, and it’s especially common in hot weather, on long flights, or during desk-bound workdays. The fix is straightforward: get up and move around at least once an hour. The swelling typically goes down once you elevate your legs or start walking, which activates the calf muscles that help pump fluid back toward your heart.
Ankle Sprains and Injuries
An injury is usually obvious, but even a minor twist you barely noticed can produce noticeable swelling hours later. Ankle sprains are graded by severity, and the amount of swelling tracks closely with how much ligament damage occurred.
- Grade 1 (stretched ligament): Mild swelling and tenderness with no joint instability. You can still bear weight. Recovery takes 1 to 3 weeks.
- Grade 2 (partial tear): Moderate swelling, possible bruising, and some loss of range of motion. Recovery takes 3 to 6 weeks.
- Grade 3 (full tear): Severe swelling, significant bruising, and inability to walk. Recovery can take several months.
For the first 24 to 48 hours after an injury, rest the ankle and avoid heat, including hot showers and heat packs, which increase swelling. Cold compresses and elevation work better in this early stage.
Chronic Venous Insufficiency
Your leg veins have one-way valves that keep blood moving upward toward your heart. When those valves weaken or get damaged, blood flows backward and pools in the lower legs, a condition called chronic venous insufficiency. It affects about 1 in 20 adults, and roughly 1 in 3 adults has varicose veins, which are a related and sometimes precursor condition.
The swelling from venous insufficiency tends to worsen over the course of the day and improve overnight. Left untreated, the rising pressure in your leg veins can burst tiny capillaries, turning the skin reddish-brown. Over time, the skin becomes fragile and vulnerable to open sores called venous stasis ulcers. In severe cases, trapped fluid causes scar tissue to form in the calf, making it feel large and hard.
Blood Clots
A blood clot in a deep leg vein, known as deep vein thrombosis (DVT), is one of the more urgent causes of ankle swelling. The key distinguishing feature: it almost always affects one leg, not both. Along with swelling, you may notice pain or cramping that starts in the calf, warmth in the affected area, and skin that looks red or purple.
DVT matters because a clot can break loose and travel to the lungs. If you develop sudden shortness of breath, chest tightness or pain, coughing up blood, a racing heartbeat, or feel faint and clammy alongside leg swelling, that combination suggests a clot may have reached your lungs. This is a medical emergency.
Heart, Kidney, and Liver Disease
When ankle swelling is caused by an organ not working properly, it usually affects both legs and develops gradually over weeks or months rather than appearing overnight.
In congestive heart failure, one or both lower chambers of the heart stop pumping blood effectively. Blood backs up in the veins, and fluid is pushed into the tissues of the legs, ankles, and feet. The swelling often comes with shortness of breath, fatigue, and difficulty lying flat.
Kidney disease prevents the body from clearing excess fluid and salt from the blood. The resulting swelling typically shows up in the legs and around the eyes. A related condition called nephrotic syndrome damages the kidney’s tiny filtering vessels, causing protein to leak out of the blood. That protein loss pulls even more fluid into the tissues.
Liver damage from cirrhosis causes fluid buildup both in the abdominal area (a condition called ascites) and in the legs. If you have known liver disease and your ankles start swelling, it’s a sign the liver is struggling to produce the proteins that keep fluid inside your blood vessels.
Medication Side Effects
Certain blood pressure medications are well-known culprits. Calcium channel blockers, a category that includes some of the most commonly prescribed blood pressure drugs, cause ankle swelling in 1 to 15% of patients at standard doses. At higher doses taken long-term, that number can climb above 80%. The swelling happens because these drugs relax blood vessels, which allows more fluid to leak into surrounding tissues.
Interestingly, combining these medications with another type of blood pressure drug can cut the swelling rate roughly in half. In one trial, patients taking a calcium channel blocker alone had a swelling rate of about 19%, while those taking it in combination with another agent had a rate closer to 8%. If your ankles started swelling after beginning a new medication, that’s worth bringing up at your next appointment. Other drugs that can cause fluid retention include certain diabetes medications, steroids, and anti-inflammatory painkillers like ibuprofen.
Pregnancy-Related Swelling
Some ankle swelling during pregnancy is completely normal, especially in the third trimester, as the growing uterus puts pressure on veins that return blood from the legs. But a specific pattern of swelling raises a red flag for preeclampsia: sudden, excessive weight gain (more than 5 pounds in a week) combined with swelling in the face and hands rather than just the ankles. If your rings suddenly don’t fit or your face looks puffy alongside rising blood pressure, those are more specific warning signs than ankle swelling alone.
Lymphedema
Your lymphatic system is a network of vessels that drains fluid from tissues and routes it back into the bloodstream. When that system gets blocked or damaged, fluid accumulates and causes persistent swelling. This is lymphedema, and it most often develops as a consequence of cancer treatment. Surgery that removes lymph nodes, radiation therapy that creates scar tissue, or a tumor itself can all disrupt lymph flow.
People treated for vulvar, vaginal, ovarian, endometrial, cervical, prostate, or colorectal cancer are particularly at risk for lymphedema in the legs. It can also develop after surgery for melanoma or sarcoma. Other risk factors include being overweight, having an infection during recovery, and slow wound healing after surgery. Unlike most other causes of ankle swelling, lymphedema tends to be chronic and requires ongoing management to keep fluid from accumulating.
How Doctors Assess Swelling Severity
If you visit a doctor for ankle swelling, they’ll likely press a finger into the swollen area for several seconds. If the pressure leaves an indentation that doesn’t bounce right back, that’s called pitting edema, and it’s graded on a 1 to 4 scale based on how deep the pit is and how long it takes to fill back in.
- Grade 1: A 2 mm dent that rebounds immediately.
- Grade 2: A 3 to 4 mm dent that rebounds within 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 2 to 3 minutes to fill back in.
This grading helps determine how much fluid has accumulated and guides decisions about what testing to pursue next. Grade 1 in someone who’s been sitting all day is very different from grade 4 in someone with no obvious explanation.