Classification Terminology and Definitions in Reporting of MRI in Axial Spondyloarthritis

Spondyloarthritis (SpA) is a group of chronic inflammatory conditions which severely impact quality of life. Several criteria have been developed in the past to aid the diagnosis of SpA based on symptoms and radiographic changes during the course of the disease. However, it takes several years before structural changes manifest on conventional radiographs, leading to a diagnostic delay of 6 to 10 years. The use of MRI and its incorporation into the Assessment of Spondyloarthritis (ASAS) criteria, has radically changed the diagnosis of SpA in the last decade by allowing visualisation of both active and chronic inflammatory changes and enabling clinicians to recognise SpA during it's early stage and initiate treatment. An understanding of the various terminology used in the divisions of disease presentations and their relevant imaging findings are key, along with the use of clear definitions of structural and inflammatory changes on MRI, in ensuring accurate diagnosis and classification of SpA.