This study investigated athletes presenting with grade II syndesmosis injuries and identified the clinical and radiological factors important in differentiating a stable from dynamically unstable injury and those findings associated with a longer recovery and return to sport.

Sixty-four athletes were prospectively assessed with an average follow-up of 37 months (range 24–66 months). Athletes with an isolated distal syndesmosis (+/− medial deltoid ligament) injury were included. Those athletes with a concomitant ankle fracture were excluded. Those considered stable (grade IIa) were treated conservatively with a boot and progressive rehabilitation. Those with clinical signs of instability underwent arthroscopy and if instability was confirmed (grade IIb) the syndesmosis was stabilized surgically. The clinical assessment of injury to individual ligaments of the ankle and syndesmosis were recorded along with MRI findings, complications and time to return to play.

All athletes returned to the same level of professional sport – 28 with IIa injuries returned at a mean of 45 days whereas the 36 with grade IIb injuries returned to play at a mean of 64 days (p< 0.001). Clinical assessment of injury to the ligaments of the syndesmosis correlated well with MRI findings. Those with a positive squeeze test were 9.5 times as likely and those with a deltoid injury 11 times more likely to have an unstable syndesmosis confirmed arthroscopically. The combination of injury to the AITFL and deltoid ligament was associated with a delay in return to sport. Concomitant injury to the ATFL indicated a different mechanism of injury with the syndesmosis less likely to be unstable and was associated with an earlier return to sport.

Clinical and MRI findings may differentiate stable from dynamically unstable grade II injuries and identify which athletes may benefit from early arthroscopic assessment and stabilization. It also suggests the timeframe for expected return to play.