Figure 2. 16-year-old female ballet dancer. (a) Sagittal spin echo T1 weighted MR image (TR/TE, 722/20) shows an os trigonum with excess soft tissue being compressed between the calcaneum and the posterior plafond of the talus, in keeping with posterior ankle impingement syndrome. (b) Sagittal short tau inversion recovery (TR/TE/TI, 4655/30/130) shows the localized oedema in the os trigonum, adjacent talus and the soft tissues in keeping with posterior ankle impingement syndrome.