"Non-radiographic axial spondyloarthritis" is a term used to describe patients with symptomatic SpA who do not have findings on plain x-rays. These patients can have identical symptoms to those with radiographic evidence of cartilage loss and erosions, and anti-TNF (anti-Tumor Necrosis Factor) therapy has been shown to be effective in those with non-radiographic SpA.8 These patients are a clinically relevant subgroup, as 20% of patients with only MRI evidence of sacroiliitis will progress to non-reversible radiographic SpA over two years.9 Therefore, MRI evidence of sacroiliitis, in conjunction with inflammatory back pain is now sufficient to diagnosis SpA. In fact, MRI imaging is a standard component of current SpA diagnostic criteria, (ASAS: Assessment of SpondyloArthritis International Society),10 and MRI changes of sacroiliitis are routinely used to identify SpA patients for clinical trials.11