Fig. 1

Multi-modality representation of typical imaging findings in ankylosing spondylitis (AS). Morphological MRI findings (a–d) and radiographical findings (e) are demonstrated. a–c Sagittal short tau inversion recovery (STIR, a), T1-weighted (T1w, b), and T2-weighted (T2w, c) images of the lumbar spine (T12–S2) of a 31-year-old male with r-axSpA. Typical disease-related changes are acute inflammation of vertebral corners (a) that are visible as multi-segmental focal signal hyperintensities of the anterior and posterior corners of vertebral endplates (white arrows in a). Signs of chronic inflammation, i.e., fatty infiltration, of the vertebral endplate corners are detected as signal hyperintensities in T1w and T2w images (white arrows in b and c). d, e Sagittal T1w image (obtained laterally at the height of the neuroforaminal openings) and lateral radiographic projection of the lumbar spine of a 46-year-old male with AS. Here, chronic inflammation at a vertebral endplate corner is visible as a focal signal hyperintensity (block arrow in d) or focal sclerosis (block arrow in e) of the upper anterior corner of the vertebral body of L5. New bone formations can be seen as bridging syndesmophytes (arrowheads) and as transdiskal ankylosis (white arrows)