Background: Patients with fibromyalgia (FM) frequently resort to osteopathic or chiropractic treatment, despite very weak supporting evidence. We aimed to assess the efficacy of osteopathic manipulation in FM in a properly controlled and powered randomized clinical trial.

Methods: Patients were randomized to osteopathic or sham treatment. Treatment was administered by experienced physical medicine physicians, and consisted of six sessions per patient, over 6 weeks. Treatment credibility and expectancy were repeatedly evaluated. Patients completed standardized questionnaires at baseline, during treatment, and at 6, 12, 24, and 52 weeks after randomization. The primary outcome was pain intensity (100-mm visual analog scale) during the treatment period. Secondary outcomes included fatigue, functioning, and health-related quality of life. We performed primarily intention-to-treat analyses adjusted for credibility, using multiple imputation for missing data.

Results: In total, 101 patients (94% women) were included. Osteopathic treatment did not significantly decrease pain relative to sham treatment (mean difference during treatment: -2.2 mm; 95% confidence interval, -9.1 to 4.6 mm). No significant differences were observed for secondary outcomes. No serious adverse events were observed, despite a likely rebound in pain and altered functioning at week 12 in patients treated by osteopathy. Patient expectancy was predictive of pain during treatment, with a decrease of 12.9 mm (4.4-21.5 mm) per 10 points on the 0-30 scale. Treatment credibility and expectancy were also predictive of several secondary outcomes.

Conclusion: Osteopathy conferred no benefit over sham treatment for pain, fatigue, functioning, and quality of life in patients with FM. These findings do not support the use of osteopathy to treat these patients. More attention should be paid to the expectancy of patients in FM management.