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Child Orthopedics
Spine - Cervical
Spine - Lumbar
Spine - Thoracic

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I am a very active, athletic 54-year old. I've been trying to strengthen my knees because I'm starting to get painful knee arthritis. So far, my efforts haven't done anything to improve things. Why not?

Muscle weakness is common with knee osteoarthritis. At first, scientists thought this was just linked with pain. Pain leads to inactivity, which leads to muscle atrophy and weakness. But further studies have shown there may be more to it than that. A specific mechanism referred to as arthrogenous muscle inhibition (AMI) may be a key factor. This refers to an inhibition of motoneurons in and around the affected joint. Efforts to restore strength are unsuccessful even for people who don't have joint pain. Research is now focused on finding ways to interrupt or inhibit the firing of these signals that inhibit muscle function. One of those ways may be with static magnetic field (magnet) therapy. The results of a recent 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. The main focus of the 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. 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. 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.


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