A critical overview of the imaging arm of the ASAS criteria for diagnosing axial spondyloarthritis: what the radiologist should know.

Spondyloarthritis (SpA) traditionally encompasses ankylosing spondylitis, psoriatic arthritis, arthritis associated with inflammatory bowel disease, arthritis associated with acute anterior uveitis, reactive arthritis, and undifferentiated SpA (1). In terms of clinical presentation, SpA may be predominantly axial (i.e., with involvement of the sacroiliac joints and/or the spinal column) or peripheral in location. The first decade of the new millennium saw significant progress in the management of axial spondyloarthritis in large part due to the use of tumor necrosis factor (TNF) antagonists in therapy. The objective verification of disease activity is even more important now, not only in terms of the initial diagnosis of SpA, but also for monitoring the response to treatment. Magnetic resonance imaging (MRI) can reveal pre-radiographic disease and may predict the subsequent develop