Patients with axial spondyloarthritis are classified according to the 2009 Assessment of SpondyloArthritis international Society classification criteria—which are the basis for the differentiation between the classical ankylosing spondylitis or radiographic axial spondyloarthritis and non-radiographic axial spondyloarthritis—on the basis of the presence or absence of definite radiographic changes in the sacroiliac joints.1 Although the clinical significance of this difference has been challenged,2 the two subsets have been accepted by the European Medicines Agency, which has led to the approval of biologicals for non-radiographic axial spondyloarthritis in Europe but not in the USA to date.