Objectives To assess whether the site of axial pain (thoracic spine, lumbar spine or buttock(s)) was associated with the site of MRI lesions in patients with recent inflammatory back pain (IBP) suggesting spondyloarthritis.

Methods We conducted a cross-sectional study of baseline data in 708 patients with recent IBP from the DESIR cohort. Radiographs of the sacroiliac joints (SIJs) and MRI scans of the SIJs and thoracic and lumbar spine were obtained routinely. Associations between pain sites and sites of inflammatory and structural MRI changes were evaluated using separate multivariate logistic regressions.

Results Of the 648 patients with complete data, 61% had thoracic pain, 91.6% lumbar pain and 79.2% buttock pain. MRI inflammation was seen in 19%, 21% and 46% of patients at the thoracic, lumbar and SIJ sites, respectively. By multivariate analysis, pain was significantly associated with MRI inflammation only at the same site (adjusted OR (aOR)_{thoracic pain} 1.71; 95% CI 1.09 to 2.67; p=0.02; aOR_{lumbar pain} 2.53; 95% CI 1.03 to 6.20; p=0.04; aOR_{buttock pain} 2.86; 95% CI 1.84 to 4.46; p<0.0001). Pain site was not significantly associated with the site of structural MRI changes, except for buttock pain and SIJ structural MRI changes (aOR_{buttock pain} 1.89; 95% CI 1.22 to 2.90; p=0.004). The association between pain site and site of MRI inflammation persisted in the subgroups with normal or doubtful SIJ radiographs or with Assessment of SpondyloArthritis international Society criteria for axial spondyloarthritis.

Conclusions The site of pain (thoracic spine, lumbar spine or buttock(s)) is associated with MRI inflammation at the same site in patients with recent IBP.