RESUMO
OBJECTIVES: To test the effectiveness of a typical magnetic wrist strap for reducing pain and stiffness, and for improving physical functioning amongst patients with osteoarthritis. DESIGN: A randomised double-blind placebo-controlled crossover trial. Each participant wore four devices over a 16-week period. SETTING: Forty five patients with osteoarthritis were recruited from general practices in rural and urban areas of Yorkshire. INTERVENTIONS: Experimental device: a commercially available magnetic wrist strap. Control devices: a weak magnetic wrist strap, a demagnetised wrist strap, and a copper bracelet. MAIN OUTCOME MEASURES: The WOMAC Osteoarthritis Index, the McGill Pain Questionnaire-Pain Rating Index (PRI), a pain visual analogue scale (VAS), and medication use. RESULTS: No difference was observed between devices in terms of their effects on pain as measured by the primary outcome measure (WOMAC A), the PRI and the VAS. Similar results were obtained for stiffness (WOMAC B), physical function (WOMAC C), and medication use. Further analyses of the PRI subscales revealed a statistically significant difference between devices (P=0.025), which favoured the experimental device. Participants reported lower sensory pain after wearing the standard magnetic wrist strap, than when wearing control devices. However, no adjustment was made for multiple testing. CONCLUSIONS: Our results indicate that magnetic and copper bracelets are generally ineffective for managing pain, stiffness and physical function in osteoarthritis. Reported therapeutic benefits are most likely attributable to non-specific placebo effects. However such devices have no major adverse effects and may provide hope.
