<qa>  What is one of the most burdensome health problems in prevalence and cost of care?Chronic, non-specific low back pain is among the most burdensome health problems in both prevalence and cost of care. Up to one third of acute low back pain cases may become chronic and lead to disability. A large fraction of chronic cases are absent of findings of well-understood causes, i.e. neoplastic, infectious or inflammatory conditions, or nerve compression, and are generally designated as uncomplicated, non-specific, or mechanical. Usual care typically includes oral and injected medication, physical therapy and exercise. Therapeutic response is difficult to predict and many outcomes are unsatisfactory, with high rates of relapse. 