Moderators of the Effects of Exercise and Manual Therapy for People With Knee and Hip Osteoarthritis: A Secondary Analysis of a Randomized Clinical Trial.

Abstract

This study aimed to investigate potential moderators influencing the effects of manual therapy and exercise therapy on pain and functional outcomes in individuals with knee and/or hip osteoarthritis, using data from the MOA trial. This is a secondary analysis of data from the MOA trial that compares the clinical effectiveness of manual therapy and/or exercise therapy in addition to usual care for patients with hip and/or knee osteoarthritis. A total of 206 participants were analyzed. The primary outcome measure was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) composite score after one year. The secondary outcome measures were WOMAC pain and function scores. We used linear regression models for assessing whether the effect of randomized interventions on pain and function was moderated by body mass index (BMI), pain self-efficacy, quadriceps strength, mental health, and education. BMI moderated the treatment effects of manual therapy interventions on WOMAC composite (β -4.1, 95% confidence interval [CI] -6.6 to -1.7), function (β -3.3, 95% CI -5.1 to -1.6), and pain scores (β -0.6, 95% CI -1.3 to 0.0) when compared to usual care. A negative β reflects an improvement in outcome associated with each one-unit increase in BMI. Mental health moderated (β 16.8, 95% CI 2.2-31.4) treatment effects of manual therapy interventions when compared to usual care. No other moderation effect was identified. Our findings suggest manual therapy may prove to be a more suitable treatment for people with higher BMI and should undergo further trials. Future trials should continue to explore which variables moderate treatment effects when testing effectiveness of nonsurgical interventions in patients with hip or knee osteoarthritis.