Back pain is one of the most common health complaints,affecting 8 out of 10 people at some point during their lives. The lower back is the area most often affected. For many people,back pain goes away on its own after a few days or weeks. But for others,the pain becomes chronic and lasts for months or years. Low-back pain can be debilitating,and it is a challenging condition to diagnose,treat,and study. The total annual costs of low-back pain in the United States—including lost wages and reduced productivity—are more than $ 100 billion.