Several myths hold sway in popular misperceptions about back pain.
Actually, problems with discs arise in fewer than 5 percent of back injuries, and the discs never slip. Instead, discs herniate or bulge and protrude, causing pain by pinching the nerves that run along the spine. But even this association with back pain has been recently called into question. In 1994, a study by researchers at Hoag Memorial Hospital in Newport Beach, California, of magnetic resonance imaging ,or MRI , of the lower back in patients who reported no back pain found that only one-third of the study participants had normal discs. The rest of the group either had bulging discs or discs that protruded beyond the vertebrae.