Compensation Worsens Back Pain

B O S T O N, Dec. 4, 2001 -- When your foot hurts, you limp and use other muscles to avoid pain and prevent further damage. But when your back is injured, that same kind of compensation may actually increase your chances of being reinjured.

Researchers now report in the Dec. 1 issue of the journal Spine that injured subjects unconsciously inflicted twice the twisting force and 1 ½ times the compressive force on the spine than uninjured subjects when lifting the same object.

The study compared the lifting activity of 22 adults with lower back pain to that of 22 adults with no back injury.

"To support any activity with the back, typically you only use one or two [of the muscles supporting the spine]," says William Marras, professor of biodynamics at Ohio State University and lead author of the study.

"What we found is when people get injured, they use not only the back muscles, but they use all the rest of the supportive muscles as well and all of those things contribute to the compressive load on the spine," he adds.

And experts are concerned that this use of compensatory muscles and compressive force could ultimately lead to further back injuries down the road.

High Cost of Back Injury

The idea that other muscles are compensating for injured back muscles is not new, but up until this point, there has been no scientific evidence that this was in fact the case.

"We have known that for years intuitively," says Dr. Robert Bray, a spine surgeon and director of the institute for spinal disorders for the Cedars Sinai Medical Center. "This study is a nice demonstration of what many people have believed for years."

"Overcompensation is not a good thing, but it is a natural thing," says Lisa Ferrara, director of the Spine Research Laboratory at the Cleveland Clinic Foundation.

Recognizing overcompensation as a factor in future back injury and preventing reinjury may have many economic and physical implications.

"Back pain is the most common cause for which an adult person seeks medical care," says Bray. "That and the flu or colds are the [most common] reasons why people miss work."