The effect of the relationship (therapeutic alliance) between patients and physical therapists on treatment outcome in the rehabilitation of patients with chronic low back pain (LBP) has not been examined before. This study, a retrospective observational study nested within a randomised controlled trial, had the objective to investigate whether the therapeutic alliance between physical therapists and patients with chronic LBP predicts clinical outcomes. One hundred eighty-two patients with chronic LBP who volunteered for a randomised controlled trial that compared the effectiveness of exercises and spinal manipulative therapy rated their alliance with physical therapists by completing the Working Alliance Inventory at the second treatment session. The primary outcomes of function, global perceived effect of treatment, pain, and disability were assessed before and after 8 weeks of treatment. The therapeutic alliance was consistently a predictor of results for all the measures of treatment outcome. The therapeutic alliance moderated the effect of treatment on global perceived effect for 2 of 3 treatment contrasts (general exercise versus motor control exercise, spinal manipulative therapy versus motor control exercise).
The study found that positive therapeutic alliance ratings between physical therapists and patients are associated with improvements of outcomes in LBP. Future research should examine the factors explaining this relationship and the effect of training interventions aimed at optimizing the alliance.