Swollen Feet and Ankles: Common Causes and When to Worry

Your shoes feel tight by afternoon. Your ankles look puffy. You press a finger into the swollen area and it leaves an indent that takes a few seconds to fill back in. Foot and ankle swelling — medically called peripheral edema — is incredibly common, and most of the time it's benign. But sometimes it's a warning sign of something that needs attention.

The challenge is knowing which category your swelling falls into. Understanding the common causes and recognizing red flags can help you make that distinction.

Benign Causes of Foot Swelling

Prolonged standing or sitting. Gravity pulls fluid downward throughout the day. If you stand for work, sit at a desk for hours, or take a long flight, fluid accumulates in the lower extremities. This is the most common cause of end-of-day foot swelling and is usually symmetric (both feet equally).

Heat. Blood vessels dilate in warm weather to release heat, which allows more fluid to leak into surrounding tissues. Southern California summers are particularly notorious for this.

High sodium intake. Excess dietary sodium causes your body to retain water. A salty meal can produce noticeable swelling the following day.

Pregnancy. Normal pregnancy causes significant fluid retention, especially in the third trimester. The growing uterus also compresses the inferior vena cava, impeding venous return from the legs. Mild, symmetric swelling is expected — but sudden or severe swelling warrants immediate obstetric evaluation for preeclampsia.

Post-exercise swelling. Vigorous activity, especially on hard surfaces, can cause temporary inflammatory swelling in the feet. This typically resolves within hours.

Musculoskeletal Causes

Ankle sprains and fractures cause acute, localized swelling from tissue damage and inflammation. The swelling is usually one-sided and accompanied by pain, bruising, and difficulty bearing weight.

Tendinitis — particularly of the posterior tibial tendon or peroneal tendons — can produce swelling along the course of the affected tendon. The swelling tends to worsen with activity.

Arthritis causes joint-specific swelling. Gout produces dramatic, rapid-onset swelling of the big toe joint with intense redness and pain. Rheumatoid arthritis causes symmetric joint swelling, often affecting the smaller toe joints. Osteoarthritis produces more gradual swelling associated with stiffness.

Stress fractures produce localized swelling on top of the foot, often without a clear injury. The area is tender to direct pressure.

Venous and Lymphatic Causes

Chronic venous insufficiency is extremely common, especially with age. The one-way valves in the leg veins become incompetent, allowing blood to pool rather than returning efficiently to the heart. This produces chronic, bilateral swelling that worsens with standing and improves with elevation. You may notice visible varicose veins, skin discoloration around the ankles, or thickened skin over time.

Deep vein thrombosis (DVT) is a blood clot in the deep veins of the leg. It typically produces unilateral swelling — one leg noticeably larger than the other — along with warmth, redness, and calf tenderness. DVT is a medical emergency because the clot can break loose and travel to the lungs (pulmonary embolism). Risk factors include recent surgery, prolonged immobility, cancer, and clotting disorders.

Lymphedema occurs when the lymphatic system can't adequately drain fluid from the extremities. It can be primary (genetic) or secondary (after lymph node removal, radiation, infection, or surgery). The swelling tends to be non-pitting (doesn't leave an indent when pressed) and progressive without treatment.

Systemic Causes

Heart failure reduces the heart's ability to pump blood effectively, causing fluid to back up in the venous system. The resulting bilateral swelling is often worse at the end of the day and accompanied by other symptoms like shortness of breath, fatigue, or weight gain from fluid retention.

Kidney disease impairs the body's ability to filter and excrete excess fluid and sodium, leading to generalized edema that often appears first in the feet and around the eyes.

Liver disease reduces production of albumin, the protein that helps keep fluid inside blood vessels. Low albumin causes fluid to leak into tissues, producing edema.

Medications are an underrecognized cause of foot swelling. Calcium channel blockers like amlodipine are particularly common culprits. NSAIDs, corticosteroids, certain diabetes medications, and hormone therapies can also contribute.

Red Flags: When Swelling Needs Urgent Attention

Most foot swelling is benign, but certain patterns require prompt evaluation. Sudden, unilateral swelling (one leg much more swollen than the other) could indicate DVT. Swelling accompanied by chest pain, shortness of breath, or difficulty breathing could signal pulmonary embolism or heart failure. Swelling with redness, warmth, and fever suggests infection — particularly concerning in patients with diabetes. Sudden severe swelling in pregnancy could indicate preeclampsia. Swelling that develops rapidly after starting a new medication warrants a call to your prescribing physician.

When to See a Podiatrist

A podiatric evaluation is appropriate when foot or ankle swelling is accompanied by pain suggesting a musculoskeletal cause, follows an injury and you're unable to bear weight, persists despite elevation, compression, and reduced sodium, is associated with skin changes around the ankle, or affects your ability to wear shoes or walk comfortably. We can evaluate the musculoskeletal components, identify biomechanical contributors, and coordinate with your primary care physician if the swelling suggests a systemic cause that needs further workup.

Managing Benign Swelling

For swelling without red flags, several strategies help. Elevate your feet above heart level for 20–30 minutes several times daily. Compression socks (15–20 mmHg) counteract gravity-driven fluid pooling. Regular walking activates the calf muscle pump that helps push fluid back toward the heart. Reducing sodium intake below 2,300 mg daily limits fluid retention. Staying well-hydrated — counterintuitively — helps your kidneys excrete excess sodium and fluid. And limiting prolonged static positions (set a timer to get up every 30–60 minutes if you sit for work) keeps the circulation moving.

If conservative measures aren't controlling your swelling, or if you notice any of the red flags described above, it's time for an evaluation. Swelling is your body's signal that something is happening — and figuring out what is the first step toward resolving it.