Long-term MRI outcomes of the phase III RAPID-axSpA study demonstrate that early improvements in spinal and sacroiliac joint inflammation achieved following treatment with certolizumab are maintained to week 204, with similar responses in patients with ankylosing spondylitis and those with non-radiographic axial spondyloarthritis. Assessment of sacroiliac joint radiographs showed limited overall progression over 4 years, with most progression observed during years 0–2 as compared with years 2–4 of the study.