Juvenile idiopathic arthritis (JIA) is a chronic inflammatory disease that affects joint function, resulting in significant effects on quality of life by limiting physical and psychosocial integration1. JIA has an estimated worldwide prevalence of 0.07 to 4.01 cases and an incidence rate of 0.008 to 0.226 cases per 1000 children per year, respectively, highlighting the global disease burden and the need for new clinical trials for JIA management2.

Magnetic resonance imaging (MRI) has been reported to be sensitive in detecting early inflammatory changes in the sacroiliac joints (SIJ) in JIA long before radiography, thus allowing for intervention before the onset of irreversible joint damage. Clinical assessment of the SIJ is limited by its location and anatomy. The quantification of interval change of pediatric SIJ using an MRI-based scoring method may serve as an important objective outcome measure.