What is the recommended approach for investigating an ankle ligament injury?

Investigation of Ankle Ligament Injury

For suspected ankle ligament injuries, apply the Ottawa Ankle Rules immediately to determine if radiographs are needed to rule out fracture, then delay the definitive ligament assessment with the anterior drawer test until 4-5 days post-injury for optimal diagnostic accuracy. 1

Immediate Assessment: Rule Out Fracture

Apply Ottawa Ankle Rules First

• Use the Ottawa Ankle Rules as your primary screening tool with sensitivity of 86-99% and negative predictive value of 97-99% to determine need for radiographs 1
• Order radiographs if ANY of the following are present:
  • Pain on palpation at the posterior edge (6 cm) of the lateral or medial malleolus 1
  • Pain on palpation at the base of the fifth metatarsal bone 1
  • Pain on palpation of the navicular bone 1
  • Inability to bear weight immediately after injury AND in the emergency department (cannot walk at least four steps) 1

Alternative Decision Rules

• The Leiden ankle rules (sensitivity 88%, specificity 57%) and Utrecht ankle rules (sensitivity 59%, specificity 84%) exist but offer no clear advantage over Ottawa Ankle Rules 1
• Do NOT use the Bernese ankle rules as sensitivity is too low (69-86%) for clinical use 1

Ligament Injury Assessment: Timing is Critical

Acute Phase (First 48 Hours)

• Physical examination in the first 48 hours CANNOT reliably distinguish between simple distortion and complete ligament rupture due to excessive swelling and pain 1
• Document presence of hematoma and pain on palpation around the distal fibula, but defer definitive ligament testing 1
• Apply compression bandage, advise elevation and ankle movements (especially dorsiflexion), and allow weight-bearing as tolerated 2

Delayed Physical Examination (4-5 Days Post-Injury)

• Perform the anterior drawer test at 4-5 days post-injury when sensitivity (84%) and specificity (96%) are optimized 1
• The combination of four findings indicates likely lateral ligament rupture:
  • Hematoma present 1
  • Pain on palpation around distal fibula 1
  • Positive anterior drawer test 1
  • Significant swelling 3

Grading System

• Grade I: Mild sprain with minimal functional loss 1
• Grade II: Moderate sprain with microligament lesions 1
• Grade III: Severe sprain with complete ligament rupture 1

Advanced Imaging: When and What to Order

Ultrasonography

• Has similar sensitivity (92%) to delayed physical examination but lacks specificity (64%) 1
• Depends heavily on technician experience and equipment availability 1
• Not recommended as first-line investigation given superior performance of delayed clinical examination 1

MRI Indications

• Reserve MRI for specific clinical scenarios, not routine ankle sprains 1:
  • Suspected high-grade ligament injuries requiring surgical planning 1
  • Suspected osteochondral defects 1
  • Suspected syndesmotic injuries 1
  • Suspected occult fractures 1
  • Persistent symptoms after initial treatment period 1
• MRI has excellent sensitivity (93-96%) and specificity (100%) for visualizing these injuries 1
• Do NOT order MRI for suspected uncomplicated anterior talofibular ligament rupture as delayed physical examination is sufficient 1

Obsolete Tests to Avoid

• Do NOT use stress radiographs: limited diagnostic value and cause unnecessary pain in acute setting 1
• Do NOT use arthrography: invasive procedure with no better accuracy than delayed physical examination 1

Special Considerations

Syndesmotic (High Ankle) Sprains

• Perform crossed-leg test: apply pressure to medial side of knee and assess for pain in syndesmosis area 3
• Consider MRI if syndesmotic injury suspected as these require different management 3

Recurrent Injuries

• Previous ankle sprain is a significant risk factor for re-injury 3
• Persistent inability to return to previous activity level or recurrent swelling with activity suggests re-injury or incomplete healing 3
• Consider MRI to evaluate for underlying joint damage in chronic cases 1

Common Pitfalls to Avoid

• Do not rely on immediate post-injury physical examination to diagnose ligament rupture—wait 4-5 days 1
• Do not order radiographs on every ankle injury—apply Ottawa Ankle Rules systematically 1
• Do not order MRI routinely—reserve for specific indications listed above 1
• Do not assume bilateral ankle swelling is traumatic—consider systemic causes like cardiac, renal, or medication-related edema 4