Magnetic shoe insoles did not effectively relieve foot pain

Sep 26 2005

Magnetic shoe insoles did not effectively relieve foot pain among patients in a study, researchers report in the current issue of Mayo Clinic Proceedings. And the results indicate that patients who strongly believed in magnets had pain relief even if they were given false magnets to wear.

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

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

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

Otherwise, the fact that magnetic and nonmagnetic insoles provided nearly identical pain relief suggests that it may have been simply the cushioning that was effective -- and not the magnets.

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

Magnetic devices use either static or pulsed magnets. Clinically, pulsed magnets have been shown effective for treating delayed fracture healing, for reducing pain in various musculoskeletal conditions, and for decreasing edema associated with acute trauma, although other studies have shown no benefit in these situations. Externally applied static magnets generally are considered safe and have few adverse effects, but little is known about their mechanism of action. Most basic scientific research has focused on movement 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 the arch of the foot. These insoles were chosen because they are comfortably cushioned but do not have rigid arch support or acupressure features, which potentially could confound results if such features provided an independent effect. The special set of false magnetic insoles also were produced by the manufacturer, using a nonmagnetized metal foil embedded identically in the foam insole material.

Along with Dr. Winemiller, Edward Laskowski, M.D., and W. Scott Harmsen of Mayo Clinic, collaborated on this study, as did Robert Billow, D.O., who is now with Northwest Orthopaedic Surgeons, Mount Vernon, Wash.

This project was funded by an unrestricted educational grant from the Spenco Medical Corp, Waco, Texas. Spenco was not involved in any way in the study design, data collection, data analyses, or data interpretation or in manuscript preparation, review or approval. Both the active and false magnetic insoles were provided at no charge directly from the manufacturer. None of the authors have any affiliations or financial involvement with any organization or entity with a financial interest in the subject matter discussed in this article.

In an editorial in the same issue, Roger Fillingim, Ph.D., and Donald Price, Ph.D., of the University of Florida College of Dentistry in Gainesville noted how the placebo controls of the study was important.

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