Magnetic resonance imaging findings associated with posterior ankle impingement syndrome are prevalent in elite ballet dancers and athletes

Objective: To report the prevalence of MRI features commonly associated with posterior ankle impingement syndrome in elite ballet dancers and athletes and to compare findings between groups. Materials and methods: Thirty-eight professional ballet dancers (47.4% women) were age- and sex-matched to 38 elite soccer or cricket fast bowler athletes. All participants were training, playing, and performing at full workload and underwent 3.0-T standardised magnetic resonance imaging of one ankle. De-identified images were assessed by one senior musculoskeletal radiologist for findings associated with posterior ankle impingement syndrome (os trigonum, Stieda process, posterior talocrural and subtalar joint effusion-synovitis, flexor hallucis longus tendon pathology and tenosynovitis, and posterior ankle bone marrow oedema). Imaging scoring reliability testing was performed. Results: Posterior talocrural effusion-synovitis (90.8%) and subtalar joint effusion-synovitis (93.4%) were common in both groups, as well as the presence of either an os trigonum or Stieda process (61.8%). Athletes had a higher prevalence of either os trigonum or Stieda process than dancers (74%, 50% respectively, P = 0.03). Male athletes had a higher prevalence of either os trigonum or Stieda process than male dancers (90%, 50% respectively, P = 0.01), or female athletes (56%, P = 0.02). Posterior subtalar joint effusion-synovitis size was larger in dancers than athletes (P = 0.02). Male and female dancers had similar imaging findings. There was at least moderate interobserver and intraobserver agreement for most MRI findings. Conclusion: Imaging features associated with posterior impingement were prevalent in all groups. The high prevalence of os trigonum or Stieda process in male athletes suggests that this is a typical finding in this population.