Effect of Magnetic Knee Wrap on Quadriceps Strength in Patients With Symptomatic Knee Osteoarthritis

Abstract 

Chen C-Y, Chen C-L, Hsu SC-C, Chou S-W, Wang K-C. 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±8.6y) 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°/s (P=.007) and 60°/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 (.05Nm/kg vs −.09Nm/kg at 60°/s, P=.038) and week 12 (30°/s, .09Nm/kg vs .04Nm/kg, P=.044; 60°/s, .17Nm/kg vs .02Nm/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.

Key Words: Magnetics, Muscle strength, Osteoarthritis, knee, Quadriceps muscle, Rehabilitation

List of Abbreviations: AMI, arthrogenous muscle inhibition, CV, coefficient of variation, ES, effect size, HAQ, Health Assessment Questionnaire, HAQ-DI, Health Assessment Questionnaire Disability Index, ITT, intention-to-treat, IQR, interquartile range, mT, mTesla, NSAID, nonsteroidal anti-inflammatory drug, OA, osteoarthritis, ROM, range of motion, SMF, static magnetic field, VAS, visual analog scale, WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index