Moll, J. M. & Wright, V. Psoriatic arthritis. Semin. Arthritis Rheum. 3, 55–78 (1973).

Article  CAS  PubMed  Google Scholar 

Jadon, D. R. et al. Axial disease in psoriatic arthritis study: defining the clinical and radiographic phenotype of psoriatic spondyloarthritis. Ann. Rheum. Dis. 76, 701–707 (2017).

Article  PubMed  Google Scholar 

Feld, J. et al. Is axial psoriatic arthritis distinct from ankylosing spondylitis with and without concomitant psoriasis? Rheumatology 59, 1340–1346 (2020).

Article  PubMed  Google Scholar 

Kwok, T. S. H. et al. Isolated axial disease in psoriatic arthritis and ankylosing spondylitis with psoriasis. Ann. Rheum. Dis. 81, 1678–1684 (2022).

Article  PubMed  Google Scholar 

Baeten, D. et al. Risankizumab, an IL-23 inhibitor, for ankylosing spondylitis: results of a randomised, double-blind, placebo-controlled, proof-of-concept, dose-finding phase 2 study. Ann. Rheum. Dis. 77, 1295–1302 (2018).

Article  PubMed  Google Scholar 

Deodhar, A. et al. Three multicenter, randomized, double-blind, placebo-controlled studies evaluating the efficacy and safety of ustekinumab in axial spondyloarthritis. Arthritis Rheumatol. 71, 258–270 (2019).

Article  CAS  PubMed  Google Scholar 

Siebert, S., Millar, N. L. & McInnes, I. B. Why did IL-23p19 inhibition fail in AS: a tale of tissues, trials or translation? Ann. Rheum. Dis. 78, 1015–1018 (2019).

Article  PubMed  Google Scholar 

McGonagle, D., Watad, A., Sharif, K. & Bridgewood, C. Why inhibition of IL-23 lacked efficacy in ankylosing spondylitis. Front. Immunol. 12, 614255 (2021).

Article  CAS  PubMed  PubMed Central  Google Scholar 

Deodhar, A. et al. Guselkumab in patients with active psoriatic arthritis who were biologic-naive or had previously received TNFα inhibitor treatment (DISCOVER-1): a double-blind, randomised, placebo-controlled phase 3 trial. Lancet 395, 1115–1125 (2020).

Article  CAS  PubMed  Google Scholar 

Mease, P. J. et al. Guselkumab in biologic-naive patients with active psoriatic arthritis (DISCOVER-2): a double-blind, randomised, placebo-controlled phase 3 trial. Lancet 395, 1126–1136 (2020).

Article  CAS  PubMed  Google Scholar 

Ramiro, S. et al. ASAS-EULAR recommendations for the management of axial spondyloarthritis: 2022 update. Ann. Rheum. Dis. 82, 19 (2023).

Article  PubMed  Google Scholar 

Coates, L. C. et al. Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA): updated treatment recommendations for psoriatic arthritis 2021. Nat. Rev. Rheumatol. 18, 465–479 (2022).

Article  PubMed  PubMed Central  Google Scholar 

Sieper, J. et al. New criteria for inflammatory back pain in patients with chronic back pain: a real patient exercise by experts from the Assessment of SpondyloArthritis international Society (ASAS). Ann. Rheum. Dis. 68, 784–788 (2009).

Article  CAS  PubMed  Google Scholar 

Bennett, A. N. et al. Severity of baseline magnetic resonance imaging-evident sacroiliitis and HLA-B27 status in early inflammatory back pain predict radiographically evident ankylosing spondylitis at eight years. Arthritis Rheum. 58, 3413–3418 (2008).

Article  CAS  PubMed  Google Scholar 

Haddad, A., Thavaneswaran, A., Toloza, S., Chandran, V. & Gladman, D. D. Diffuse idiopathic skeletal hyperostosis in psoriatic arthritis. J. Rheumatol. 40, 1367–1373 (2013).

Article  PubMed  Google Scholar 

Gladman, D. D. Axial psoriatic arthritis. Curr. Rheumatol. Rep. 23, 35 (2021).

Article  PubMed  Google Scholar 

Poddubnyy, D. et al. Axial Involvement in Psoriatic Arthritis cohort (AXIS): the protocol of a joint project of the Assessment of SpondyloArthritis international Society (ASAS) and the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA). Ther. Adv. Musculoskelet. Dis. 13, 1759720X211057975 (2021).

Article  PubMed  PubMed Central  Google Scholar 

Benjamin, M. & McGonagle, D. The anatomical basis for disease localisation in seronegative spondyloarthropathy at entheses and related sites. J. Anat. 199, 503–526 (2001).

Article  CAS  PubMed  PubMed Central  Google Scholar 

Bollow, M. et al. Early sacroiliitis in patients with spondyloarthropathy: evaluation with dynamic gadolinium-enhanced MR imaging. Radiology 194, 529–536 (1995).

Article  CAS  PubMed  Google Scholar 

Hermann, K. G. & Bollow, M. Magnetic resonance imaging of sacroiliitis in patients with spondyloarthritis: correlation with anatomy and histology. RoFo 186, 230–237 (2014).

PubMed  Google Scholar 

van der Linden, S., Valkenburg, H. A. & Cats, A. Evaluation of diagnostic criteria for ankylosing spondylitis. A proposal for modification of the New York criteria. Arthritis Rheum. 27, 361–368 (1984).

Article  PubMed  Google Scholar 

Ridley, L. K. et al. Why do some patients have severe sacroiliac disease but no syndesmophytes in ankylosing spondylitis? Data from a nested case-control study. J. Rheumatol. 50, 335–341 (2022).

PubMed  Google Scholar 

Oostveen, J., Prevo, R., den Boer, J. & van de Laar, M. Early detection of sacroiliitis on magnetic resonance imaging and subsequent development of sacroiliitis on plain radiography. A prospective, longitudinal study. J. Rheumatol. 26, 1953–1958 (1999).

CAS  PubMed  Google Scholar 

Puhakka, K. B. et al. Magnetic resonance imaging of sacroiliitis in early seronegative spondylarthropathy. Abnormalities correlated to clinical and laboratory findings. Rheumatology 43, 234–237 (2004).

Article  CAS  PubMed  Google Scholar 

Bollow, M. et al. Very early spondyloarthritis: where the inflammation in the sacroiliac joints starts. Ann. Rheum. Dis. 64, 1644 (2005).

Article  CAS  PubMed  PubMed Central  Google Scholar 

Appel, H. et al. Correlation of histopathological findings and magnetic resonance imaging in the spine of patients with ankylosing spondylitis. Arthritis Res. Ther. 8, R143 (2006).

Article  PubMed  PubMed Central  Google Scholar 

Marzo-Ortega, H., O’Connor, P., Emery, P. & McGonagle, D. Sacroiliac joint biopsies in early sacroiliitis. Rheumatology 46, 1210–1211 (2007).

Article  CAS  PubMed  Google Scholar 

Gracey, E. et al. Tendon and ligament mechanical loading in the pathogenesis of inflammatory arthritis. Nat. Rev. Rheumatol. 16, 193–207 (2020).

Article  PubMed  PubMed Central  Google Scholar 

Romero-López, J. P., Elewaut, D., Pacheco-Tena, C. & Burgos-Vargas, R. Inflammatory foot involvement in spondyloarthritis: from tarsitis to ankylosing tarsitis. Front. Med. 8, 730273 (2021).

Article  Google Scholar 

Pacheco-Tena, C. et al. Bone lineage proteins in the entheses of the midfoot in patients with spondyloarthritis. J. Rheumatol. 42, 630–637 (2015).

Article  PubMed  Google Scholar 

Marzo-Ortega, H. et al. Baseline and 1-year magnetic resonance imaging of the sacroiliac joint and lumbar spine in very early inflammatory back pain. Relationship between symptoms, HLA-B27 and disease extent and persistence. Ann. Rheum. Dis. 68, 1721–1727 (2009).

Article  CAS  PubMed  Google Scholar 

McGonagle, D. et al. The role of biomechanical factors and HLA-B27 in magnetic resonance imaging-determined bone changes in plantar fascia enthesopathy. Arthritis Rheum. 46, 489–493 (2002).

Article  PubMed  Google Scholar 

Lambert, R. G. W. et al. High prevalence of symptomatic enthesopathy of the shoulder in ankylosing spondylitis: deltoid origin involvement constitutes a hallmark of disease. Arthritis Care Res. 51, 681–690 (2004).

Article  Google Scholar 

Braun, J., Bollow, M. & Sieper, J. Radiologic diagnosis and pathology of the spondyloarthropathies. Rheum. Dis. Clin. North Am. 24, 697–735 (1998).

Article  CAS  PubMed  Google Scholar 

Baraliakos, X. et al. Frequency of MRI changes suggestive of axial spondyloarthritis in the axial skeleton in a large population-based cohort of individuals aged <45 years. Ann. Rheum. Dis. 79, 186–192 (2020).

Article  PubMed  Google Scholar 

Caetano, A. P., Mascarenhas, V. V. & Machado, P. M. Axial spondyloarthritis: mimics and pitfalls of imaging assessment. Front. Med. 8, 658538 (2021).

Article  Google Scholar 

Baraliakos, X., Listing, J., Rudwaleit, M., Sieper, J. & Braun, J. The relationship between inflammation and new bone formation in patients with ankylosing spondylitis. Arthritis Res. Ther. 10, R104 (2008).

Article  PubMed  PubMed Central  Google Scholar 

Ball, J. Enthesopathy of rheumatoid and ankylosing spondylitis. Ann. Rheum. Dis. 30, 213–223 (1971).

Article  CAS  PubMed  PubMed Central  Google Scholar 

Chung, H. Y., Yiu, R. S. W., Chan, S. C. W., Lee, K. H. & Lau, C. S. Fatty corner lesions in T1-weighted magnetic resonance imaging as an alternative to sacroiliitis for diagnosis of axial spondyloarthritis. BMC Rheumatol. 3, 17 (2019).

Article  PubMed  PubMed Central