MRI in spondyloarthritis: when and how?

PURPOSE OF REVIEW: To summarize recent advances and challenges of using MRI toward early recognition of axial spondyloarthritis (SpA). RECENT FINDINGS: Low-grade bone marrow edema (BME) on sacroiliac joint (SIJ) MRI is nonspecific and may be misleading in recognition of axial SpA. Structural features on SIJ MRI along with BME may not only facilitate recognition of early disease, but also enhance specificity. Structural lesions on MRI and low-dose computed tomography are highly concordant, adding to criterion validity of SIJ MRI. There is accumulating evidence that SIJ MRI due to superior reliability of structural lesions may supplant the traditional imaging approach by pelvic radiographs in healthcare settings in which MRI is readily available. Pilot initiatives exploring the bone remodeling cascade in SIJs showed early reparative response upon biological treatment. Methodological challenges regarding evaluation and data processing of imaging examinations need to be addressed to enhance reproducibility and specificity of imaging in SpA. SUMMARY: Evaluation of SIJ MRI is contextual incorporating structural lesions and BME. MRI is but one element in pattern recognition toward diagnosis. An unmet need is dissemination of advances in imaging in SpA to the broad community of rheumatologists and radiologists.