Introduction: Illness Perceptions (IPs) may play a role in the management of persistent low back pain. The mediation
and/or moderation effect of IPs on primary outcomes in physiotherapy treatment is unknown.
Methods: A multiple single-case experimental design, using a matched care physiotherapy intervention, with three
phases (phases A-B-A’) was used including a 3 month follow up (phase A’). Primary outcomes: pain intensity, physical
functioning and pain interference in daily life. Analyzes: linear mixed models, adjusted for fear of movement, catastrophizing,
avoidance, sombreness and sleep.
Results: Nine patients were included by six different primary care physiotherapists. Repeated measures on 196 data
points showed that IPs Consequences, Personal control, Identity, Concern and Emotional response had a mediation
effect on all three primary outcomes. The IP Personal control acted as a moderator for all primary outcomes, with clinically
relevant improvements at 3 month follow up.
Conclusion: Our study might indicate that some IPs have a mediating or a moderating effect on the outcome of a
matched care physiotherapy treatment. Assessing Personal control at baseline, as a relevant moderator for the outcome
prognosis of successful physiotherapy management of persistent low back pain, should be further eplored.