There has been a resurgence of interest in defining the axial inflammation component of psoriatic arthritis (PsA) since recent randomized controlled trials (RCTs) raised the possibility that this entity may respond differentially to therapeutics compared to patients with axial spondyloarthritis. A workshop was conducted during the 2021 Group for Research and Assessment of Psoriasis and Psoriatic Arthritis annual meeting to review the literature on diagnosing PsA and to determine which criteria might be most appropriate. There was quite strong agreement that magnetic resonance imaging (MRI) had an important role to play in helping to define axial inflammation in PsA and that a data-driven methodology for generating optimal MRI quantitative cut-offs for lesions in the sacroiliac joints and/or spine that reflect imaging typical of axial inflammation in PsA would be most desirable.