Principal component analysis of MRI findings. PC plots of (A) 58 patients in Groups 1–4 and (B) all 85 patients classified according to the 2017 EULAR/ACR classification criteria are presented. Each point represents each patient and is colour-coded for the subgroups. 95% probability ellipses are shown according to the subgroups. The percentage of variance explained by each component is indicated on the axis labels