Magnet Therapy for Knee OsteoarthritisThe results of this study from Taiwan showed that a magnetic knee wrap for patients with osteoarthritis is safe, effective, and low cost. Using measures of strength, pain, and function, the patients who used the magnetic wrap showed significant improvement over the control group who wore a placebo wrap.
This low-cost option for home treatment is good news for the many older adults who are limited by their knee arthritis. Getting up from a chair, walking, and going up and down stairs can be very difficult. A simple magnet wrap that can increase strength and reduce pain means better function and improved quality of life.
Since arthritis is a chronic disease and treatment with antiinflammatories can cause significant side effects, finding alternative ways to treat it is essential. Magnet therapy has been advertised for this condition, but studies are lacking to show if they are safe and effective.
Some published studies support the idea that a static electromagnetic field (SMF) can relieve pain. But there have been conflicting reports, so the data is not consistent. And in all studies, the placebo group also reported less pain when wearing a wrap without magnets.
The main focus of this study was the effect of magnetic knee wrap on quadriceps strength. In particular, isokinetic strength was measured. Isokinetic refers to strengthening the muscle throughout the range of motion. Patients included had mild-to-moderate knee osteoarthritis with chronic knee pain. The magnets used in this study were permanent and able to generate a static electromagnetic field (SMF).
Everyone wore the knee wrap daily during their waking hours for 12 weeks. If they had arthritis in both knees, the wrap was worn on the more painful knee. If both knees were equally painful, the wrap was placed on the nondominant leg. Patients were advised not to exercise or participate in strength training of any kind during the 12 weeks period of time.
The placebo wrap was the same size, shape, material, and weight as the true magnetic wrap. Usually in studies comparing magnetic vs. nonmagnetic devices, it is difficult to keep the groups from knowing who had the magnetic wrap and who didn't. Nonmagnetic material does not stick to metal objects and magnetic material does. This is a very obvious clue as to which group the subjects are in. In this study, the patients were asked not to test which was the active magnet and which was a sham.
A special device (Biodex System 3) was used to measure isokinetic strength of the quadriceps (front of thigh) muscle. Everyone performed five maximal muscle contractions without stopping at two different speeds (velocity) of movement. The machine was set for 30 degrees of motion per second and 60 degrees/second. This was the main test for strength. Patients also filled out two questionnaires (Health Assessment Questionnaire, Western Ontario and McMaster Universities Osteoarthritis Index) geared to measure pain and function.
Strength improved in the magnetic wrap group right from the start. And strength continued to improve until it peaked at the end of the 12th week. On the other hand, the control group showed no improvement and even a mild decrease in strength. Patients in both groups were equally compliant (cooperative to wear the wrap as directed).
The authors believe this was the first scientific investigation into the effect of a magnetic knee wrap to improve quadriceps muscle strength. They concluded that there may be a role for static electromagnetic field in recovering lost strength in patients with painful knee arthritis.
In fact, they suspect the way the magnetic therapy works to improve strength isn't by direct strengthening of the quadriceps muscle. They suggest that a static electromagnetic field may help turn the quadriceps muscle back on after being inhibited by changes in the nerve messages set up in response to pain signals.
The next step in exploring the use of static electromagnetic field for knee osteoarthritis is to conduct a similar study with patients who have more advanced (severe) arthritis. And a longer follow-up period for this study (and any future studies) would be helpful to see if the effects of turning off muscle inhibition associated with osteoarthritis are long-lasting.
It would be helpful to know if a short course of magnet therapy is all that's needed to get the muscle action turned around. Strengthening programs would be more effective with better results than when conducted alone. And this added information might help explain why rehab to improve motor control and function has not helped improve quadriceps strength.
It's not enough to know what kinds of physical training or treatment will improve quadriceps strength in this patient population. Which method is the fastest with the longest effects is important, too. Getting people back up on their feet with the pain relief, strength, and the endurance they need for daily activities and work is the goal.
Chung-Yao Chen, MD, et al. Effect of Magnetic Knee Wrap on Quadriceps Strength in Patients with Symptomatic Knee Osteoarthritis. In Archives of Physical Medicine and Rehabilitation. December 2008. Vol. 89. No. 12. Pp. 2258-2264.
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