Background The Canada-Denmark (CANDEN) definitions of spinal MRI lesions allow a detailed anatomy-based evaluation of inflammatory and structural lesions in vertebral bodies and posterior elements of the spine in patients with axial spondyloarthritis (axSpA). The objective was to examine the reliability, responsiveness and discrimination of scores for spinal inflammation, fat, bone erosion and new bone formation based on the CANDEN system and to describe patterns of inflammatory and structural lesions and their temporal development. Methods 49 patients with axSpA from an investigator-initiated, randomised, placebo-controlled trial of adalimumab underwent spinal MRI at weeks 0/6/24/48. MR images were scored according to the CANDEN system and the Spondyloarthritis Research Consortium of Canada (SPARCC) method. Total scores, and various subscores, were created by summing individual lesion scores. Results The CANDEN spine inflammation score had high responsiveness, similar to the SPARCC MRI spine index (Guyatt's responsiveness index 1.88 and 1.67, respectively), and discriminated between adalimumab and placebo treatment already at 6 weeks' follow-up (P=0.03). Anterior/posterior corner inflammation subscores showed similar responsiveness. Inter-reader reliability for the CANDEN spine inflammation and fat scores was good to very good for status and change scores (intraclass correlation coefficient (ICC)=0.71-0.92). Reliability for CANDEN new bone formation and erosion scores was good to very good for status scores (ICC=0.61-0.75) but, due to minimal progression, poor for change scores (ICC≤0.40). Conclusions The CANDEN spine inflammation score showed good responsiveness, discrimination between active treatment and placebo and reliability. The CANDEN spine structural scores had good cross-sectional reliability, but longer studies are needed to investigate their sensitivity to change.