Table 4.

Features of an Assessment of SpondyloArthritis Society definition of positive magnetic resonance imaging for sacroiliitis (37).

Active inflammation of subchondral or periarticular bone marrow

Active inflammation is defined as bone marrow edema on short tau inversion recovery sequences or osteitis on gadolinium-enhanced T1-weighted sequences

Two or more lesions must be present on the same coronal slice or a single lesion must be visible on two consecutive slices

Other inflammatory features of axial spondyloarthritis, such as synovitis, enthesitis, and capsulitis are believed to be rare in the absence of bone marrow edema and in isolation are not sufficient for diagnosis