With Comments from Russell H. Greenfield, MD
Magnets and Osteoarthritis
Source: Harlow T, et al. Randomised controlled trial of magnetic bracelets for relieving pain in osteoarthritis of the hip and knee. BMJ 2004;329:1450-1454.
Goal: To assess effectiveness, or lack thereof, of magnetic bracelets for pain relief in osteoarthritis (OA) of the hip and knee.
Design: Three parallel groups; randomized, placebo-controlled trial.
Subjects: One hundred ninety-four people aged 45-80 years with hip or knee OA recruited from rural general practices in Great Britain who scored at least 8-20 points on the WOMAC A osteoarthritis index.
Methods: Subjects were randomized to wear for 12 weeks either a standard-strength bipolar magnetic bracelet (170-200 mTesla), a weak magnetic bracelet (21-30 mTesla), or a non-magnetic bracelet (non-magnetic steel washers). Participants were advised they would be receiving either an active or an inactive bracelet. Outcome measures included change in WOMAC scales (A = pain, B = leg stiffness, C = functioning), and a visual analogue scale (VAS) for pain. Data were collected at 0, 4, and 12 weeks. At trial’s end all bracelets were returned and tested, and all participants were offered a full-strength magnetic bracelet.
Results: Significant differences were found for WOMAC A and C and VAS pain score with greater improvements seen in the standard magnetic bracelet group than in the non-magnetic bracelet group. No significant difference in 12-week WOMAC B change was detected among the three groups. The average strength of the standard magnets was 186 mTesla, while the non-magnetic bracelets all showed 0 strength. A significant error was identified in the production of the weak magnets (some were stronger than expected).
Conclusions: Magnetic bracelets are effective at relieving pain from OA of the hip and knee as compared with placebo bracelets.
Study strengths: Blinding of participants and providers; testing of the three types of bracelets to assure uniformity of intervention; the few subjects lost to follow-up were evenly spread among the three groups; reported compliance close to 100% during waking hours.
Study weaknesses: Manufacturing error with weak magnets (34 of the weak magnets were actually strong with a mean of 128 mTesla); manner of ascertaining compliance (VAS at 4 and 12 weeks); short duration of trial.
Of note: The majority of participants were Caucasian; there exist significant differences between the strength and types of magnets used therapeutically, as well as the recommended durations of application; the strength of the weak magnets was designed to be enough to appear to be magnetic, but not sufficient to be therapeutic (intended to provide placebo, but the manufacturing error prevented objective assessment of placebo effect); WOMAC B score has been shown to lack specificity; the reduction in WOMAC A and C scores for the active group approximate those previously found with nonsteroidal anti-inflammatory drugs (NSAIDs) and exercise therapy for OA.
We knew that: One in 13 people in the United States has OA; worldwide sales of static magnetic devices in 1999 reached approximately $5 billion; whereas some studies have suggested therapeutic benefit with static magnets (specifically for pain relief), others have not; field strength plays a significant role in potential efficacy, as studies that failed to show a beneficial effect for pain relief used weaker magnets (19-50 mTesla), while those reporting significant pain reduction used magnets with strengths of 47-180 mTesla; although magnetic bracelets can be expensive (as much as $100), the cost compares favorably with that of pain medications and anti-inflammatory agents.
Clinical import: This creative study addresses areas of both need and controversy, namely pain relief for those suffering with OA and the therapeutic use of magnets, respectively.
With regard to the former there can be no doubt, especially in a time when people with OA are desperate to find an effective replacement for the COX-2 inhibitors so rudely taken from them. Skepticism has surrounded the use of magnets, at least among conventionally minded practitioners, in large part due to major methodological flaws in some of the published trials, as well as the widely held perception that the entire idea of magnets as therapeutic aid is groundless.
Nonetheless, our patients utilize magnets, often unbeknownst to us, and perhaps claim benefit from them. Although the data are far from conclusive, this paper provides much needed information we can use both to discuss magnet therapy and guide those who are interested in experiencing it. Identification of readily available product from credible manufacturers, however, remains a challenge.
What to do with this article: Keep a hard copy in your file cabinet.
Dr. Greenfield, Medical Director, Carolinas Integrative Health Carolinas HealthCare System Charlotte, NC, Clinical Assistant Professor, School of Medicine, University of North Carolina, Chapel Hill, NC, is Executive Editor of Alternative Medicine Alert.