One-Sided (Unilateral) Ankle Swelling

Common Causes

1. Injury / Trauma (most common)

• Ankle sprain - the most frequent cause. The lateral ankle ligaments (especially the ATFL - anterior talofibular ligament) are torn by an inversion + plantarflexion injury. Swelling, bruising, and tenderness appear on the lateral side. - Textbook of Family Medicine 9e
• Bone fracture - malleolar (medial or lateral) fractures cause localised swelling with point tenderness. Ottawa Ankle Rules guide X-ray decisions.
• Sudeck's atrophy (Complex Regional Pain Syndrome) - post-traumatic condition with swelling, pain, skin changes. Mentioned specifically as a cause of unilateral ankle swelling. - S. Das Manual on Clinical Surgery

2. Deep Vein Thrombosis (DVT) - RED FLAG

• A blood clot in the leg veins causes unilateral leg and ankle swelling. Classified as a "strong" (+++) sign for DVT/PE in emergency medicine. - Rosen's Emergency Medicine
• Risk factors: recent surgery, trauma, immobility, cancer, pregnancy, oral contraceptives, long travel.
• Urgent - if suspected, needs Doppler ultrasound same day. Can be life-threatening due to pulmonary embolism risk.

3. Phlebothrombosis / Venous Insufficiency

• Clot or incompetent venous valves impair blood return, causing fluid to pool around the ankle. Often associated with varicose veins. - S. Das Manual on Clinical Surgery

4. Cellulitis / Infection

• Bacterial skin infection causes red, warm, tender swelling, often with fever. Usually involves one limb at a time.

5. Gout / Arthritis

• Gout causes sudden, intensely painful swelling, often in the first MTP joint but can affect the ankle. Typically one-sided and episodic.
• Septic arthritis - infected joint; presents with fever, hot swollen joint, inability to bear weight. Emergency.

6. Lymphedema

• Blockage of lymph vessels causes painless, pitting then non-pitting swelling. Lymphedema praecox (primary) is unilateral in 70% of cases and often starts around the ankle extending upward. - Andrews' Diseases of the Skin

7. Tendon / Soft Tissue Problems

• Tibialis posterior tendon rupture - medial ankle swelling + flatfoot deformity, inability to do single-leg toe raise. - Rosen's Emergency Medicine
• Peroneal tenosynovitis - swelling below and behind the lateral malleolus, pain on foot inversion. - S. Das Manual on Clinical Surgery
• Tailor's bursa - adventitious bursa over the lateral malleolus in people who sit cross-legged.

8. Ankle Joint Disease

• TB of the ankle - rare; restricted movement, bone rarefaction on X-ray, possible sinus formation.
• Osteoarthritis - chronic, gradual swelling with stiffness and limited range of motion.

Warning Signs - Seek Urgent Care

Initial Assessment Approach

1. History - onset (sudden vs gradual), trauma, travel, medications (e.g. calcium channel blockers cause ankle edema), fever, prior clots
2. Examination - compare both ankles, check for pitting, warmth, tenderness location, skin color, range of motion
3. Investigations as indicated:
   • X-ray if trauma suspected (Ottawa Ankle Rules)
   • Doppler ultrasound if DVT suspected
   • Blood tests: CBC, CRP, uric acid, D-dimer

Treatment

• Sprain: RICE (Rest, Ice, Compression, Elevation), NSAIDs, physiotherapy
• DVT: Anticoagulation (heparin/LMWH, then warfarin or a DOAC)
• Cellulitis: Antibiotics
• Gout: NSAIDs, colchicine, urate-lowering therapy
• Fracture: Immobilisation, possible surgery

Treatment of Unilateral Ankle Swelling

1. Ankle Sprain / Ligament Injury

• NSAIDs (ibuprofen, naproxen) for pain and swelling
• Functional bracing - reduces recurrence better than rest alone
• Physiotherapy - balance and proprioception training, peroneal strengthening - critical for preventing re-injury
• Surgical intervention is not indicated for most sprains - Swanson's Family Medicine Review

2. Deep Vein Thrombosis (DVT) - Medical Emergency

• Anticoagulation for at least 3 months (minimum for proximal DVT) to prevent pulmonary embolism
  • Options: LMWH (low molecular weight heparin e.g. enoxaparin), then transition to:
    • DOACs: rivaroxaban, apixaban (preferred now)
    • Warfarin (older option, requires INR monitoring)
• Thrombolysis may be considered in severe cases with massive clot
• Compression stockings after acute phase to prevent post-phlebitic syndrome
• Elevation of the limb
• Do NOT massage the leg - risk of dislodging the clot

3. Cellulitis / Skin Infection

• Oral antibiotics for mild-moderate cases: penicillin-based (flucloxacillin, amoxicillin-clavulanate) or cefalexin - Andrews' Diseases of the Skin
• IV antibiotics + hospitalization for severe cellulitis, bullae, fever, or elderly patients
• Local: rest, elevation, cool compresses
• Treat any underlying skin break or fungal infection (e.g. athlete's foot) to prevent recurrence
• Duration: at least 10 days

4. Gout (Acute Attack)

• NSAIDs (e.g. indomethacin, naproxen) - first-line for most patients
• Colchicine - highly specific for gout; effective if started within 36 hours of attack onset - Lippincott Illustrated Reviews: Pharmacology
• Oral corticosteroids (e.g. prednisolone) - if NSAIDs/colchicine are contraindicated
• Long-term: once the acute attack settles, start urate-lowering therapy:
  • Allopurinol (xanthine oxidase inhibitor) - standard
  • Febuxostat - alternative
  • Note: starting urate-lowering drugs during an acute attack can worsen it; always cover with colchicine or NSAIDs when initiating

5. Lymphedema

• Complex Decongestive Therapy (CDT) - gold standard:
  • Manual lymphatic drainage (MLD)
  • Multi-layer short-stretch compression bandaging
  • Exercises
  • Skin care
• Compression garments for long-term maintenance
• Pneumatic compression pumps - adjunct
• Surgical options (microsurgery/lymph node transfer) in refractory cases

6. Ankle Fracture

• Undisplaced fractures: cast immobilisation for 6-8 weeks, non-weight bearing
• Displaced/unstable fractures: surgical fixation (ORIF - open reduction and internal fixation)
• Elevation to control swelling; ice in first 48 hours
• Physiotherapy after cast removal for rehabilitation

7. General Measures for Any Cause of Ankle Swelling

• Elevate the leg above heart level when resting
• Avoid prolonged standing or sitting in one position
• Compression stockings (class I or II) if no arterial disease
• Gentle exercise / ankle pumps to activate the calf muscle pump
• Reduce salt intake (limits fluid retention)
• Stay hydrated - paradoxically, dehydration worsens fluid pooling

When to Go to Hospital Immediately

• Calf pain + swelling after travel/surgery/immobility - possible DVT
• Swelling + chest pain or shortness of breath - possible pulmonary embolism
• Hot, red, fever - infection or septic arthritis
• Trauma + inability to bear weight - possible fracture
• Sudden severe pain in the joint - septic arthritis or acute gout