What is the appropriate evaluation and management for a patient presenting with pain at the right external ankle suggestive of an ankle sprain, including when to order an X-ray and the components of a physical exam?

Evaluation and Management of Right External Ankle Pain

Use the Ottawa Ankle Rules to determine if X-ray is needed: order radiographs only if the patient has bony tenderness at the posterior edge or tip of the lateral malleolus, bony tenderness at the base of the fifth metatarsal, bony tenderness at the navicular bone, or inability to bear weight for four steps both immediately after injury and in your office. 1

When to Order X-Ray

The Ottawa Ankle Rules are the gold standard decision tool with 86-99% sensitivity and 97-99% negative predictive value for detecting fractures 1, 2. This means if the rules are negative, you can confidently skip radiographs and avoid unnecessary imaging in 85% of ankle injuries 1.

Order ankle radiographs if ANY of the following are present:

• Pain on palpation at the posterior edge (within 6 cm) of the lateral malleolus 1
• Pain on palpation at the base of the fifth metatarsal bone 1
• Pain on palpation of the navicular bone 1
• Inability to walk at least four steps immediately after injury AND in the emergency department/clinic 1

Do NOT order radiographs if Ottawa Ankle Rules are negative - no imaging is indicated in this scenario 1.

Physical Examination for Right External Ankle Pain

Immediate Assessment (Day 0-2)

Inspection:

• Assess for swelling, particularly around the lateral malleolus and distal fibula 3, 2
• Look for hematoma formation, which suggests more severe ligament injury 1, 2
• Check for visible deformity or gross instability 1

Palpation:

• Palpate the posterior edge of the lateral malleolus (within 6 cm from tip) for bony tenderness 1
• Palpate the base of the fifth metatarsal for tenderness 1
• Palpate the area around the distal fibula for soft tissue tenderness 1, 2
• Palpate the area just inferior to the lateral malleolus - swelling here may indicate a snowboarder's fracture (lateral talar process fracture) that can be missed on routine X-rays 40-50% of the time 1

Functional Assessment:

• Test ability to bear weight and walk four steps 1
• Assess for inability to complete jumping and landing, which is a negative prognostic factor 1

Critical Pitfall: Do NOT attempt the anterior drawer test or talar tilt test in the acute phase (first 48 hours) - excessive swelling and pain make these tests unreliable and unable to distinguish between simple sprain and complete rupture 2.

Delayed Assessment (Day 4-5 Post-Injury)

This is when ligament assessment becomes accurate. 1, 2

Anterior Drawer Test:

• Stabilize the distal tibia with one hand while grasping the heel with the other 1
• Apply anterior force to the heel while the ankle is in slight plantar flexion 1
• Positive test (excessive anterior displacement of talus) indicates anterior talofibular ligament tear 3, 2
• At 4-5 days post-injury, this test has 84% sensitivity and 96% specificity 1, 2

Crossed-Leg Test:

• Apply pressure to the medial side of the knee while the injured leg is crossed over the other 3
• Pain in the syndesmosis area indicates high ankle (syndesmotic) sprain 3

Four findings together indicate likely complete lateral ligament rupture:

• Hematoma present 1, 2
• Pain on palpation around distal fibula 1, 2
• Positive anterior drawer test 1, 2
• Significant swelling 1, 2

Grading and Prognostic Factors

Ankle sprains are classified as Grade I (mild), Grade II (moderate/microligament lesions), or Grade III (severe/complete ligament rupture) 1.

Negative prognostic factors to document:

• Previous ankle sprain history (most common risk factor for new injury) 3, 2
• High level of current pain 1
• High workload and level of sports participation 1
• Inability to complete jumping and landing within 2 weeks 1

Advanced Imaging Indications

Reserve MRI for specific scenarios only:

• Suspected high-grade ligament injuries with persistent symptoms 1, 2
• Suspected osteochondral defects 1, 2
• Suspected syndesmotic injuries 1, 2
• Occult fractures 1, 2
• Symptoms persisting beyond expected recovery time 1, 2

MRI has 93-96% sensitivity and 100% specificity for these injuries but is not needed for uncomplicated anterior talofibular ligament rupture since delayed physical examination is sufficient 1, 2.

Ultrasound has 92% sensitivity but only 64% specificity and depends on technician expertise - not recommended as first-line 1, 2.

Stress radiographs and arthrography are obsolete - do not use 1.