Many of the 50 million Americans with arthritis suffer from debilitating joint pain, often for years. Now a therapy originally developed to ease the pain caused by limbs that have been lost offers them some hope of relief.
The technique, known as mirror box therapy, is used to treat phantom limb pain experienced by amputees, a phenomenon in which the missing limb feels as if it is locked in an agonizingly uncomfortable position. Relying on the idea that there is a strong visual component to pain, phantom limb patients are asked to look at the reflection of a healthy limb in a mirror that has been placed where the missing limb should be.
Seeing the healthy limb go through normal movements seems to correct the confused signals between the brain and nerves, thereby reducing pain. In some subjects, it has proven surprisingly effective for clearing up phantom limb pain entirely.
In an as-yet unpublished study, researchers at the University of California at San Diego applied the mirror technique to patients with osteoarthritis or rheumatoid arthritis. The scientists overlaid the image of a healthy hand over the sufferer's painfully disabled hand and asked them to follow a series of slow, deliberate movements.
"Many of the patients reported a reduction in pain and stiffness during this illusion," said lead researcher Laura Case. Case, who works in the lab of Vilayanur S. Ramachandran, one of the originators of the therapy, said the team must complete additional work on mirror training for arthritis before they can say it will have long-term benefits.
Their research builds on work performed last year by psychologists at the University of Nottingham. Using a similar technique known as "illusory manipulation" in which a computer, a video screen and illustrations distort the size of a limb much as a fun-house mirror would, they tested on a group of twenty seniors with painful arthritis to see whether it would have any effect. After one session, 85 percent of participants said their pain was cut in half and six reported their pain had completely vanished -- though there was no follow up to see how long the pain reduction lasted.
Dr. Jack Tsao, associate professor of neurology at the Uniformed Services University of the Health Sciences, who works with military amputees, said the arthritis study does make a certain amount of sense. "No one knows for sure whether there is a visual aspect to the pain of arthritis, but there certainly could be. From the phantom limb work we're doing, it suggests that it may be a very deep component," he said.
Tsao points to experiments where the mirror is covered as amputee subjects go through the motions of mimicking a normal limb; without sight to guide them, far fewer report a reduction in pain -- and some report that it actually makes the pain worse.
And interestingly, in a 2009 study performed by Tsao and colleagues at Walter Reed Military Hospital, they added a group of subjects who were asked to close their eyes and merely visualize moving their missing limb without the aid of a mirror. In this case, the number and length of the phantom limb pain episodes decreased by 100 percent in the group using the mirror, by 17 percent in the covered mirror group, and by 33 percent in the mental visualization group. When the patients in the mental visualization and covered mirror groups were switched over to the mirror method, they experienced significant decreases in pain too.
These studies suggest that the sensation of pain is caused by more than just the physical components of inflammation and swelling; it may be that conditions such as arthritis might improve without painkillers and conventional therapy. Besides phantom limb pain, mirror box has also been used successfully to treat complex pain syndromes and paralysis due to stroke.
Experts say visual-based treatments like mirror box and illusory manipulation may not be introduced into mainstream arthritis therapy for some time. However, considering no medications have been proven effective for changing the overall course of osteoarthritis, and interventions such as exercise and weight loss appear to offer only limited relief, it's seen as promising alternative for those for those who struggle with the pain and disability of the disease.