“People often think of low-back pain as not that serious,” says Roger Chou, director of the Pacific Northwest Evidence-based Practice Center at Oregon Health & Science University. “Maybe it hurts, but it’s more of a nuisance than anything.” But low-back pain has an enormous impact, he notes. “Globally, it’s one of the leading causes of disability. And in the United States, it’s one of the main reasons why people go to the doctor.” What causes back pain?