What is the appropriate diagnostic approach for a high ankle sprain in a young, active athlete who sustained a sudden external‑rotation injury with proximal ankle pain and difficulty weight‑bearing?

Diagnosis of High Ankle Sprain

For a young athlete with proximal ankle pain, difficulty weight-bearing, and suspected high ankle sprain from external rotation injury, begin with standard three-view ankle radiographs (AP, lateral, mortise), and if these are negative but clinical suspicion remains high based on positive squeeze test or external rotation stress test, proceed directly to MRI without IV contrast to visualize syndesmotic ligament disruption and associated injuries.

Initial Clinical Assessment

The diagnosis starts with recognizing key clinical features that distinguish high ankle sprains from common lateral ankle sprains:

• Mechanism of injury: External rotation of the foot with the ankle dorsiflexed, or direct collision forces 1, 2
• Pain location: Proximal ankle pain above the joint line, along the syndesmosis
• Provocative maneuvers:
  • Squeeze test: Compression of the tibia and fibula at mid-calf reproduces pain distally at the syndesmosis 2, 3
  • External rotation stress test: External rotation of the foot with the knee flexed reproduces syndesmotic pain 2, 4, 3
  • Fibular shuck test: Anterior-posterior translation of the fibula relative to the tibia 2

Critical pitfall: These injuries are frequently missed on initial evaluation because standard radiographs may appear normal in subtle or latent syndesmotic instability 2. A high index of suspicion based on mechanism and physical examination findings is essential 5.

Imaging Algorithm

Step 1: Initial Radiographs

Standard three-view ankle radiographs (anteroposterior, lateral, and mortise views) are the appropriate first imaging study when Ottawa Ankle Rules are positive 6. Weight-bearing views are preferred when possible, as they provide physiologic stress that may reveal subtle syndesmotic widening 4.

Look for:

• Widening of the medial clear space (>4 mm suggests instability)
• Tibiofibular clear space widening
• Tibiofibular overlap abnormalities
• Associated fractures (Weber B/C fibular fractures, Maisonneuve pattern)

Step 2: Advanced Imaging When Radiographs Are Negative

When radiographs are negative but physical examination suggests syndesmotic injury (positive squeeze test, external rotation test, or proximal tenderness), MRI ankle without IV contrast is the appropriate next study 6. The ACR Appropriateness Criteria (2020) specifically designate MRI as "usually appropriate" for this scenario (Variant 6) 6.

MRI is superior to CT for soft-tissue evaluation and directly visualizes the syndesmotic ligament complex 6. MRI provides:

• Direct visualization of anterior inferior tibiofibular ligament (AITFL), interosseous ligament (IIOL), and posterior inferior tibiofibular ligament (PITFL) 1
• Assessment of ligament healing phases
• Detection of associated injuries (deltoid ligament tears, osteochondral lesions, bone contusions)
• Prognostic information for management decisions 2

Key MRI interpretation points 1:

• The AITFL fails first, usually at the fibular attachment
• Assess primarily in sagittal and coronal planes (axial plane is limited due to ligament obliquity)
• The IIOL typically fails toward the tibial attachment
• The PITFL fails at the inferior lateral border of the tibial attachment

Alternative: Weight-Bearing CT

Weight-bearing CT can assess syndesmotic alignment and has been studied for subtle instability 2, 4, though MRI remains superior for soft-tissue evaluation 6. CT is more useful when fracture characterization is needed after radiographs show osseous injury 6.

Clinical Context and Prognosis

High ankle sprains represent 1-11% of all ankle injuries in athletes but carry significant morbidity 7. They require longer recovery periods than lateral ankle sprains and have high recurrence rates 1, 7. In NCAA athletes, incidence is highest in football, wrestling, and ice hockey 7.

Common pitfall: Misdiagnosis or delayed diagnosis leads to chronic instability and prolonged disability 3, 5. Setting realistic expectations for recovery time is essential—these injuries typically require significantly longer return-to-play periods than lateral ankle sprains 1, 3.

Summary of Diagnostic Approach

1. Clinical examination: Squeeze test, external rotation stress test, proximal tenderness pattern
2. Initial imaging: Three-view weight-bearing ankle radiographs (if Ottawa Ankle Rules positive)
3. If radiographs negative but high clinical suspicion: MRI ankle without IV contrast 6, 1, 2
4. If radiographs show fracture: CT for fracture characterization or MRI for soft-tissue assessment depending on clinical needs 6

The key is maintaining high clinical suspicion based on mechanism (external rotation injury) and physical examination findings, then proceeding to MRI when radiographs are negative, as subtle syndesmotic instability is not apparent on static radiographs 2.