What are the treatment options for lateral malleolus pain and numbness after a fall with a perceived 'pop' in the ankle?

Lateral Malleolus Pain and Numbness After Fall with "Pop"

Apply the Ottawa Ankle Rules immediately to determine if radiographs are needed, then initiate functional treatment with a lace-up ankle brace and early mobilization rather than immobilization, while addressing the numbness as a potential nerve injury requiring specific evaluation. 1, 2

Immediate Diagnostic Approach

Rule Out Fracture First

• Use Ottawa Ankle Rules (OAR) as your primary decision tool with 86-99% sensitivity and 97-99% negative predictive value for excluding fractures 1

• Order radiographs if ANY of these criteria are met:

  • Pain on palpation at the posterior edge or tip of the lateral malleolus (within 6 cm) 1
  • Pain at the base of the fifth metatarsal 1
  • Pain at the navicular bone 1
  • Inability to bear weight immediately after injury and walk four steps 1

• If radiographs are indicated, obtain standard three-view ankle films (anteroposterior, lateral, and mortise views) 2, 3

• Weight-bearing radiographs are critical to assess stability—a medial clear space >4 mm indicates instability requiring different management 3

Address the Numbness Component

The "pop" with subsequent numbness suggests potential nerve involvement beyond simple ligament injury:

• Examine the distribution of numbness carefully:

  • Numbness over the dorsum of the foot (sparing first web space) suggests superficial peroneal nerve entrapment, which can occur approximately 10 cm above the lateral malleolus 4
  • Check for a Tinel sign over the anterolateral leg 4
  • Test for decreased sensation to light touch and pinprick in the affected distribution 4

• The combination of lateral malleolus pain with numbness may indicate:

  • Direct nerve trauma from the injury mechanism 4
  • Compartment syndrome (urgent surgical emergency—assess immediately)
  • Superficial peroneal nerve entrapment from soft tissue swelling 4

Treatment Algorithm

If No Fracture (Lateral Ankle Sprain)

Functional treatment is superior to immobilization for reducing morbidity and improving quality of life 2:

• Apply a lace-up ankle brace immediately—this provides better swelling reduction, fewer complications, and faster return to work compared to elastic bandages or tape 2, 3
• Begin early mobilization rather than rigid immobilization, which results in faster return to work, better patient satisfaction, and quicker return to sports 2, 3
• Incorporate exercise therapy from the start to prevent chronic ankle instability and improve long-term outcomes 2

If Avulsion Fracture of Lateral Malleolus Tip

• Functional treatment with early mobilization remains the preferred approach even for small avulsion fractures 2
• Use a lace-up ankle brace 2
• Obtain serial radiographs to confirm maintenance of alignment 2, 3
• Critical pitfall: Overly aggressive rehabilitation before adequate healing can lead to displacement or nonunion 2, 3

If Nondisplaced Lateral Malleolus Fracture

• Weight-bearing radiographs determine your management path: 3

  • Medial clear space <4 mm = stable fracture → conservative treatment with functional bracing 3
  • Medial clear space >4 mm = unstable fracture → surgical intervention required 3

• For stable fractures, follow the same functional treatment protocol as ankle sprains 3

• Watch for signs of associated ligamentous injury: medial tenderness, bruising, or swelling suggests deltoid ligament involvement requiring different management 3

Managing the Numbness

If numbness persists beyond initial swelling:

• Consider electrodiagnostic studies to evaluate for superficial peroneal nerve injury, which may show unrecordable evoked response or prolonged distal latency 4
• If entrapment syndrome is confirmed with a soft tissue bulge, Tinel sign, and persistent symptoms, surgical decompression by fasciotomy provides complete symptomatic relief 4
• Differentiate from other causes of ankle numbness including compartment syndrome (surgical emergency) and direct nerve contusion (typically resolves with conservative management) 4

Delayed Physical Examination Strategy

Do not rush ligament assessment—the anterior drawer test has optimal sensitivity (84%) and specificity (96%) when performed 4-5 days post-injury rather than acutely 1, 5

This delayed examination approach:

• Allows initial swelling and pain to subside 1
• Provides more accurate assessment than acute ultrasound (which has only 64% specificity) 1
• Eliminates need for MRI in uncomplicated anterior talofibular ligament ruptures 1

Critical Pitfalls to Avoid

• Missing occult instability: Failure to obtain weight-bearing radiographs can miss associated deltoid or syndesmotic ligament tears, leading to inappropriate conservative management of an unstable injury 3
• Overlooking nerve injury: The numbness component requires specific evaluation and may need electrodiagnostic studies if persistent 4
• Premature aggressive rehabilitation: Starting too early can cause displacement or nonunion in fractures 2, 3
• Ignoring medial-sided symptoms: Medial tenderness or swelling indicates potential deltoid ligament injury requiring stress radiographs 3

Expected Outcomes and Follow-Up

• Be realistic with patients: 5-33% will have persistent pain and instability at 1 year, and 3-34% experience recurrent ankle sprains 2, 3
• Address pain level, workload, and sports participation early, as these negatively influence recovery and increase recurrence risk 1
• Serial radiographs are essential to confirm healing progression 2, 3
• If symptoms persist beyond expected healing time, consider MRI to diagnose underlying joint damage, osteochondral defects, or occult fractures 1