Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Hills, MI. Last updated April 2026.

Ankle and leg swelling (edema) is one of the most common foot and ankle complaints, but there’s a critical distinction: swelling in both legs is usually different from swelling in only one leg. Bilateral edema is most often from systemic causes (heart failure, kidney disease, venous insufficiency). Unilateral swelling — one ankle or leg — carries a different and sometimes more urgent differential diagnosis. At Balance Foot & Ankle, Dr. Tom Biernacki evaluates ankle swelling with careful attention to distinguishing urgent from non-urgent causes.

Urgent Causes of One-Sided Ankle Swelling

Deep vein thrombosis (DVT) — A blood clot in the deep veins of the leg causes sudden, unilateral leg and ankle swelling, often with calf tenderness, warmth, and redness. DVT is a medical emergency — the clot can break off and travel to the lungs (pulmonary embolism), which can be fatal. Risk factors include recent surgery, prolonged immobility (long flight or car trip), cancer, pregnancy, oral contraceptives, and prior DVT. If DVT is suspected, go to the emergency room immediately or call your doctor for an urgent duplex ultrasound. Do not wait for a routine appointment.

Cellulitis — Bacterial skin infection causes rapid-onset unilateral swelling with significant redness, warmth, and sometimes fever. Red streaks extending up the leg indicate lymphangitis (spread of infection). Cellulitis requires prompt antibiotic treatment. Diabetic patients are at highest risk for serious cellulitis.

Ankle fracture — Swelling following foot or ankle trauma may indicate a fracture, even if weight-bearing is still possible. X-ray is essential. The Ottawa Ankle Rules guide clinical triage, but patients with significant swelling after injury should be evaluated radiographically.

Non-Urgent Causes of One-Sided Ankle Swelling

Ankle sprain — Lateral ankle sprains are the most common cause of sudden unilateral ankle swelling in active individuals. Swelling, bruising, and tenderness on the outer ankle after twisting are typical. RICE (Rest, Ice, Compression, Elevation) for the first 48–72 hours, then gradual rehabilitation. X-ray rules out fracture.

Chronic venous insufficiency (one-sided) — When vein disease is more severe in one leg, unilateral swelling results. Varicose veins, skin changes, and a history of prolonged standing are associated features. Compression stockings and vascular evaluation are indicated.

Lymphedema — Lymphatic obstruction (from previous surgery, radiation, cancer, or filariasis) causes chronic, progressive pitting edema in one extremity. Lymphedema is non-pitting once fibrosis develops. Treatment with compression therapy, manual lymphatic drainage, and specific exercises is managed by a certified lymphedema therapist.

Gout — Acute gout attacks commonly affect only one joint at a time — the big toe most frequently, but also the ankle. The affected joint is massively swollen, red, hot, and exquisitely tender. Uric acid crystal confirmation and appropriate anti-gout medication provide rapid relief.

Baker’s cyst rupture — A fluid-filled cyst behind the knee that ruptures can cause sudden calf and ankle swelling, mimicking DVT. Ultrasound distinguishes the two conditions.

Ankle Swelling Evaluation in Michigan

Never dismiss unilateral ankle swelling, especially if it appeared suddenly, is accompanied by pain, warmth, redness, or shortness of breath. Balance Foot & Ankle provides urgent same-week evaluations for ankle swelling at southeast Michigan offices. For DVT suspicion, go directly to an emergency room. Call (734) 479-6200 for non-urgent ankle swelling assessment.

Frequently Asked Questions

Concerned About Ankle Swelling?

Swelling in one leg can indicate a range of conditions from minor sprains to circulation issues. Our podiatrists provide thorough evaluation to identify the cause and create an effective treatment plan.

Clinical References

1. Ely JW, et al. “Approach to leg edema of unclear etiology.” J Am Board Fam Med. 2006;19(2):148-160.
2. Trayes KP, et al. “Edema: diagnosis and management.” Am Fam Physician. 2013;88(2):102-110.
3. Partsch H. “Compression therapy in leg oedema.” Phlebology. 2014;29(1 Suppl):87-93.

Dr. Tom Biernacki, DPM

Dr. Tom Biernacki, DPM is a double board-certified podiatrist and foot & ankle surgeon at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has reached over one million views.