Effect of magnetic knee wrap on quadriceps strength in patients with symptomatic knee osteoarthritis.

OBJECTIVE: To determine the effects of magnetic knee wrap on isokinetic quadriceps strength in patients with painful knee osteoarthritis (OA). DESIGN: Randomized, double-blinded, placebo-controlled and before-after trial. SETTING: Rehabilitation clinic in a tertiary hospital. PARTICIPANTS: Eligible patients (N=50) (mean age+/-SD, 66.0+/-8.6 y) with mild to moderate knee OA were recruited from the outpatient department and 37 (74%) completed the trial. Only 3 (6%) withdrew due to study-related adverse effects. INTERVENTIONS: Wearing the active (n=24) or sham (n=26) magnetic knee wrap for 12 weeks. MAIN OUTCOME MEASURES: The primary outcome measure was isokinetic quadriceps strength. Secondary outcome measures included the Health Assessment Questionnaire Disability Index (HAQ-DI) and the Health Assessment Questionnaire (HAQ) Pain Scale. RESULTS: Using intention-to-treat analyses, the peak isokinetic quadriceps strength increased significantly in the treated leg at 30 degrees/s (P=.007) and 60 degrees/s (P=.022) after wearing the magnetic knee wrap. Compared with baseline, the median strength increase for the treated leg in the study group significantly exceeded that in the control group at week 4 (.05 Nm/kg vs -.09 Nm/kg at 60 degrees/s, P=.038) and week 12 (30 degrees/s, .09 Nm/kg vs .04 Nm/kg, P=.044; 60 degrees/s, .17 Nm/kg vs .02 Nm/kg, P=.031). The HAQ-DI and HAQ Pain Scales improved significantly in both groups. Compared with baseline, the improvement at week 12 in terms of the HAQ-DI in the study group significantly exceeded that in the control group. CONCLUSIONS: Magnetic knee wrap may significantly facilitate isokinetic quadriceps strength in patients with mild to moderate knee OA.