80% of adults experience low back pain at some point in their lives.  About 20% of those develop chronic symptoms lasting a year or longer.   Since 2010 it ranks third among the most burdensome conditions in the U.S. in terms of mortality or poor health, only ischemic heart disease and chronic obstructive pulmonary disease ranking higher.  There are many categories of pain sources.  See the NIH Low Back Pain Fact Sheet, and the American Chiropractic Back Pain Facts and Statistics for more information.