What is the probable injury in a 15-year-old boy with a 2-week-old aversion (inward twisting) ankle injury, ongoing pain when walking, and a positive squeeze test with inward pressure applied to the distal tibia and fibula?

Syndesmotic (High Ankle Sprain) Injury

This 15-year-old boy most likely has a syndesmotic injury (high ankle sprain) based on the positive squeeze test, which indicates disruption of the distal tibiofibular syndesmosis ligaments. 1, 2

Clinical Reasoning

The squeeze test is specifically designed to detect syndesmotic injuries by applying compression to the proximal calf, which causes separation of the distal fibula and tibia, reproducing pain at the syndesmosis if the ligaments are injured 2. While the squeeze test has high specificity (88%) for syndesmotic injury, it should be interpreted alongside other clinical findings 1.

Key Diagnostic Features Present:

• Positive squeeze test: This biomechanically causes fibular-tibial separation at the ankle mortise level, stressing the injured syndesmotic ligaments 2
• Persistent pain at 2 weeks: Syndesmotic injuries characteristically have prolonged recovery compared to typical lateral ankle sprains 3
• Pain with walking: Indicates functional instability of the ankle mortise 4

Immediate Diagnostic Workup Required

Obtain three-view ankle radiographs (anteroposterior, lateral, and mortise views) immediately to assess for:

• Increased tibiofibular clear space (>6mm indicates diastasis) 4
• Decreased tibiofibular overlap 4
• Increased medial clear space (>4mm indicates instability) 5
• Associated fractures, particularly fibular fracture above the syndesmosis 5

5

Additional Clinical Tests to Perform:

• Syndesmosis ligament palpation: Highest sensitivity (92%) with negative likelihood ratio of 0.28 1
• Dorsiflexion-external rotation stress test: 71% sensitivity with negative likelihood ratio of 0.46 1
• Single leg hop test: Inability to hop has 89% sensitivity for syndesmotic injury 1

Advanced Imaging Algorithm

If radiographs are negative but clinical suspicion remains high (which is common), proceed with MRI ankle without IV contrast 5. This is critical because:

• Syndesmotic injury may not be apparent on plain radiographs 4
• MRI is superior for detecting ligamentous injuries and assessing for associated cartilage abnormalities 5, 6
• The ACR recommends MRI for persistent pain beyond 1 week with negative radiographs 5

Treatment Pathway

If No Diastasis (Most Common):

• Extended physical therapy protocol for high ankle sprain 3
• Non-weight bearing or protected weight bearing initially 3
• Expect prolonged recovery compared to lateral ankle sprains (typically 6-12 weeks) 3

If Diastasis >2mm Present:

• Surgical fixation is mandatory with syndesmotic screws or suture button devices 4, 3
• Failure to diagnose and stabilize syndesmotic disruption adversely affects outcome 4
• Anatomic reduction and proper screw positioning are critical for good clinical results 3

Critical Pitfalls to Avoid

• Missing associated deltoid ligament injury: Coexistence of deltoid ligament injury with syndesmotic injury critically destabilizes the ankle joint and requires more aggressive management 4
• Failing to obtain stress radiographs: Routine stress testing is necessary when syndesmotic injury is not apparent on standard radiographs 4
• Underestimating severity: Treating this as a simple lateral ankle sprain will result in prolonged disability and potential chronic instability 3, 1
• Inadequate immobilization: These injuries require longer periods of protection than typical ankle sprains 3