What is a Syndesmotic Injury?
A syndesmotic injury is damage to the ligaments that connect the distal tibia and fibula, forming the distal tibiofibular joint—often called a "high ankle sprain" because these ligaments sit above the standard ankle joint ligaments. 1, 2
Anatomical Structure
The syndesmosis is a fibrous joint comprised of four key ligaments that stabilize the distal tibia and fibula 3:
- Anterior tibiofibular ligament (most commonly injured) 4
- Posterior tibiofibular ligament 3
- Transverse ligament 3
- Interosseous ligament 3
These ligaments maintain the integrity of the ankle mortise, which is critical for normal weight-bearing and ankle movement 2, 3.
Clinical Significance
Even 1 mm of widening in the ankle mortise decreases the tibiotalar joint contact area by 42%, leading to instability and early osteoarthritis if untreated. 3 This makes accurate diagnosis and appropriate treatment essential for preventing long-term disability 1, 2.
Mechanism of Injury
Syndesmotic injuries typically occur through 2:
- External rotation of the foot on the leg (most common mechanism) 2
- Excessive dorsiflexion 2
- High-energy rotational forces during activities like skiing, football, soccer, and sports played on artificial turf 2
Injury Patterns
Syndesmotic injuries can present in two ways 1, 5:
- Isolated ligamentous injury (1-11% of all ankle sprains) 3
- Combined with ankle fractures (50% of Weber B fractures and nearly all Weber C fractures) 3
Grading System
MRI is the reference standard for grading syndesmotic injuries (Grade 1,2, or 3), which is critical for treatment planning and return-to-sport decisions, particularly in athletes. 4, 6
- Grade 1: Mild sprain without instability 5
- Grade 2: Moderate sprain with partial ligament tears 5
- Grade 3: Complete ligament rupture with instability 5
Why This Injury Matters
Syndesmotic injuries are frequently misdiagnosed and can cause 1, 2: