What is the appropriate workup for a patient presenting with ankle swelling?

Appropriate Workup for Ankle Swelling

The appropriate workup for ankle swelling should begin with determining whether the swelling is traumatic or non-traumatic in origin, as this fundamentally directs the diagnostic pathway and subsequent management.

Initial Assessment

For Traumatic Ankle Swelling:

• Apply the Ottawa Ankle Rules (OAR) to determine need for imaging 1:

  • Point tenderness over the malleoli, talus, or calcaneus
  • Inability to bear weight immediately and in the emergency department
  • Inability to take four steps

• If OAR positive: Obtain ankle radiographs (anteroposterior, lateral, and mortise views)

• If OAR negative: Radiography is not indicated 1

For Non-Traumatic Ankle Swelling:

• Evaluate for:
  1. Bilateral vs. unilateral swelling
  2. Pitting vs. non-pitting edema
  3. Associated symptoms (pain, redness, warmth)
  4. Duration and progression of swelling
  5. Systemic symptoms

Diagnostic Workup Algorithm

Step 1: Basic Laboratory Tests

• Complete blood count
• Comprehensive metabolic panel (including liver and kidney function)
• Urinalysis (to check for proteinuria)
• Thyroid function tests
• Inflammatory markers (ESR, CRP)

Step 2: Imaging Based on Clinical Presentation

For Traumatic Cases:

• If OAR positive: Radiographs first 1
• If radiographs negative but high clinical suspicion:
  • Consider MRI for soft tissue injuries, osteochondral lesions
  • Consider CT for complex fractures or posterior malleolar fractures 1

For Non-Traumatic Cases:

• Ultrasound: First-line imaging for suspected:

  • Deep vein thrombosis
  • Joint effusion
  • Soft tissue masses
  • Tendon pathology

• MRI: Consider when ultrasound is inconclusive or to evaluate:

  • Osteomyelitis
  • Complex soft tissue infections
  • Inflammatory arthropathies
  • Tendon or ligament pathology

Step 3: Special Considerations

For Suspected Infection:

• If subperiosteal abscess is suspected: Surgical drainage is usually appropriate 1
• For soft tissue infections: Consider aspiration for culture and sensitivity

For Suspected Vascular Issues:

• In diabetic patients or those with peripheral arterial disease:
  • Assess ankle pressure, toe pressure, or transcutaneous oxygen pressure (TcpO2)
  • Consider vascular imaging if toe pressure <30 mmHg or TcpO2 <25 mmHg 1

Management Considerations

• For traumatic ankle sprains:

  • PRICE protocol (Protection, Rest, Ice, Compression, Elevation) for acute phase
  • Functional rehabilitation with progressive exercise program 2

• For non-traumatic swelling:

  • Target underlying cause rather than simply prescribing diuretics 3
  • In older patients, consider multifactorial causes including medication side effects, chronic venous insufficiency, heart failure 3

Red Flags Requiring Urgent Evaluation

• Severe pain disproportionate to injury
• Rapidly progressive swelling
• Fever with ankle swelling
• Inability to bear weight after 48 hours
• Neurological symptoms (numbness, tingling)
• Color changes in the foot
• Pain that does not improve with time 2

Common Pitfalls to Avoid

1. Overlooking fractures by not properly applying the Ottawa Ankle Rules
2. Treating all ankle swelling with diuretics without determining the cause
3. Failing to consider systemic causes of bilateral ankle swelling
4. Missing compartment syndrome in traumatic cases
5. Overlooking medication-induced ankle swelling

Remember that ankle swelling, especially in older patients, is often multifactorial and requires thorough evaluation rather than symptomatic treatment alone 3.