Update on MRI of spondyloarthritis. part one: the sacro-iliac joint.

increased trend toward the use of advanced medical imaging for the diagnosis and assessment of SpondyloArthritis (SpA) (1, 2). MRI of the sacro-iliac (SI) joints has become a key-imaging technique for the detection of early non-radiographic axial SpA and has been shown to contribute to optimized clinical decisionmaking (3). The current paper aims at summarizing recent advances in the understanding of the disease, the questions from the clinicians, as well MRI protocols and findings in SpA. Pitfalls and differential diagnosis for SI changes will be addressed.