Non-specific low back pain is a common musculoskeletal disorder affecting 80% of people at some point in their lives. In the United States it is the most common cause of job-related disability, a leading contributor to missed work, and the second most common neurological ailment — only headache is more common. It can be acute, subacute or chronic in duration. With conservative measures, the symptoms of low back pain typically show significant improvement within a few weeks from onset.
Lower back pain may be classified by the duration of symptoms as acute, subacute and chronic. Within these classifications, there is no agreement across medical organizations for the specific duration of symptoms, but generally pain lasting less than six weeks is classified as acute, pain lasting six to 12 weeks is subacute, and more than 12 weeks is chronic.
The majority of lower back pain is referred to as non-specific low back pain and does not have a definitive cause. It is believed to stem from benign musculoskeletal problems such as muscle or soft tissues sprain or strains. This is particularly true when the pain arose suddenly during physical loading of the back, with the pain lateral to the spine. Over 99% of back pain instances fall within this category. The full differential diagnosis includes many other less common conditions.