Fear of movement and competence frustration mediate the relationship between pain catastrophising and physical function in people living with axSpA: an online cross-sectional survey

The objective of this study is to examine the contribution of pain catastrophising to Axial Spondyloarthritis (axSpA) patient's physical function and to test the mediating role of fear of movement, and uniquely, the contribution of competence frustration to the fear-avoidance model. Participants (N = 98, 70% female, M age = 45.62, SD 12.16) completed an online survey (December 2020-May 2021) distributed in the United Kingdom via the National Axial Spondyloarthritis Society (n ≈ 3500; NASS, 2019). The PROCESS SPSS macro was used to test three mediation models using percentile bootstrap 95% confidence intervals (PBCI). A significant indirect effect on the relationship between pain and physical function via fear of movement (β = 0.10, 95% PBCI = 0.030-0.183) was observed (Model 1). Model 2 showed the relationship between pain catastrophising and physical function to be significantly mediated by fear of movement (β = 0.16, 95% PBCI = 0.005-0.322). Finally, Model 3 showed a significant indirect effect on the relationship between pain catastrophising and physical function via competence frustration (β = 0.15, 95% PBCI = 0.014-0.309) but not through fear of movement (β = 0.062, 95% PBCI = - 0.134 to 0.248). To our knowledge, this is the first study to examine and demonstrate the unique contribution of competence need frustration to the Fear-avoidance model in people that live with axSpA. Identifying modifiable factors that contribute to disease outcomes such as physical function can improve the care and quality of life for people living with a disease currently without a cure.