© Copyright CliniCal and ExpErimEntal rhEumatology 2020.Objective To determine and compare the effectiveness of history, physical examination, conventional radiography and magnetic resonance imaging (MRI) in the detection of sacroiliitis in juvenile spondyloarthropathies. Methods One hundred and one patients with JSpA, 33 patients with other diseases and 24 children without rheumatologic complaints were included in the study. Subjects were evaluated using physical examination, laboratory findings, pelvic radiography and MRI. Abdominal or pelvic MRIs of 24 control patients who were obtained in the last 6 months were reevaluated and multivariate logistic regression analyses were used to calculate probability ratios of variables. Results In our study, the rate of active sacroiliitis was 52.4% and in most of them, erosive and sclerotic changes indicating destruction of the sacroiliac joints were recorded. The presence of sacroiliitis on direct x-ray, high JSPADAI score, and hip involvement on MRI were independent risk factors with high predictive potential for active sacroiliitis. Inflammatory lumbar pain, sacroiliac tenderness, modified Schober’s limitation, acute phase elevation, HLA-B27 positivity and presence of uveitis failed to predict sacroiliitis. The best specificity was 100% with a high BASFI score (>5), then 94% with a high JSPADAI score (>4). None of the patients in the control group showed active sacroiliitis. Conclusion All patients with possible JSpA should undergo sacroiliac MRI whether HLA-B27 positive or not. In this way, early diagnosis and treatment of axial joint involvement could be possible and it prevents unnecessary examination and loss of time.