OBJECTIVE: Pain and activity limitations are the main health complaints in osteoarthritis. We explored pathways between pain and activity limitations in a chain mediation model that involved self-efficacy, physical activity behavior, and muscle function in patients with hip osteoarthritis not awaiting hip replacement.

METHODS: We used cross-sectional, baseline data from a randomized controlled trial on 152 patients with clinical hip osteoarthritis according to the American College of Rheumatology not awaiting hip replacement. The associations between pain, self-efficacy, self-reported physical activity, muscle function (leg extensor power), and activity limitations (performance-based and self-reported activity limitation outcomes) were modeled using structural equation models.

RESULTS: The effect of pain on performance-based activity limitation was fully mediated by self-efficacy, physical activity, and muscle function. Of the total effect of self-efficacy on performance-based activity limitation, the direct effect accounted for 63% (95% CI: 45%-82%), whereas the indirect effect via physical activity constituted 16% (95% CI: 1%-30%) and the indirect effect via muscle function constituted 21% (95% CI: 9%-32%). In contrast, physical activity and muscle function had no effect on self-reported activity limitations, whereas pain had a direct effect and an indirect effect mediated by self-efficacy.

CONCLUSION: Our results suggest that self-efficacy should be taken into consideration in prevention and treatment of activity limitations in patients with hip osteoarthritis not awaiting hip replacement. Coupling exercise with programs of self-efficacy enhancement could potentially increase the positive effects of exercise.