Magnetic Insoles Do Not Provide Pain Relief, Mayo Clinic Study Reports

"This study provides convincing evidence that use of these staticmagnets was not effective in relieving symptoms of nonspecific footpain in the workplace," says Mark Winemiller, M.D., the lead author ofthe study and a Mayo Clinic physician.

Dr. Winemiller said adults with foot pain are likely toinitiate self-treatment with magnets based on personal recommendationsor belief systems, often without a specific diagnosis or prescription.That population was targeted in this study, he said, with the goal ofdetermining whether magnetic insoles work in the way they are typicallyused. He said the randomized, double-blind nature of this study waschosen to minimize bias and maximize the validity of results, and he isconfident that this was accomplished.

An interesting result in the study relates to "the placeboeffect." Patients in studies who are given the placebo or falsetreatment often report improvement in their conditions when theybelieve they are receiving a treatment designed to provide relief. "Amoderate placebo effect was noted in participants who believed thestrongest in the potential of magnets to help their pain," says Dr.Winemiller.

Otherwise, the fact that magnetic and nonmagnetic insolesprovided nearly identical pain relief suggests that it may have beensimply the cushioning that was effective -- and not the magnets.

In the past decade, the use of magnets for pain relief hasincreased substantially. Despite little scientific evidence (and lackof Food and Drug Administration approval for pain relief), many peoplehave used magnets to relieve their pain, spending approximately $5billion worldwide -- an estimated $500 million in the United Statesannually -- on magnetic pain-relieving devices.

Magnetic devices use either static or pulsed magnets.Clinically, pulsed magnets have been shown effective for treatingdelayed fracture healing, for reducing pain in various musculoskeletalconditions, and for decreasing edema associated with acute trauma,although other studies have shown no benefit in thesesituations. Externally applied static magnets generally are consideredsafe and have few adverse effects, but little is known about theirmechanism of action. Most basic scientific research has focused onmovement of tiny electrical voltages that may lead to decreased pain.

The insoles studied were the Active Comfort magnetic insole(Spenco Medical Corp.), which has a magnetic foil pad located under thearch of the foot. These insoles were chosen because they arecomfortably cushioned but do not have rigid arch support or acupressurefeatures, which potentially could confound results if such featuresprovided an independent effect. The special set of false magneticinsoles also were produced by the manufacturer, using a nonmagnetizedmetal foil embedded identically in the foam insole material.

Along with Dr. Winemiller, Edward Laskowski, M.D., and W. ScottHarmsen of Mayo Clinic, collaborated on this study, as did RobertBillow, D.O., who is now with Northwest Orthopaedic Surgeons, MountVernon, Wash.

This project was funded by an unrestricted educational grantfrom the Spenco Medical Corp, Waco, Texas. Spenco was not involved inany way in the study design, data collection, data analyses, or datainterpretation or in manuscript preparation, review or approval. Boththe active and false magnetic insoles were provided at no chargedirectly from the manufacturer. None of the authors have anyaffiliations or financial involvement with any organization or entitywith a financial interest in the subject matter discussed in thisarticle.

In an editorial in the same issue, Roger Fillingim, Ph.D., andDonald Price, Ph.D., of the University of Florida College of Dentistryin Gainesville noted how the placebo controls of the study wasimportant.

"Placebo controls are extremely valuable for determining the efficacy of pain interventions," the authors write.

A peer-review journal, Mayo Clinic Proceedings publishes originalarticles and reviews dealing with clinical and laboratory medicine,clinical research, basic science research and clinical epidemiology.Mayo Clinic Proceedings is published monthly by Mayo Foundation forMedical Education and Research as part of its commitment to the medicaleducation of physicians. The journal has been published for more than75 years and has a circulation of 130,000 nationally andinternationally. Copies of the articles are available online at www.mayoclinicproceedings.com.