The lower back is sometimes known as the lumbar region, where each vertebra of the spine is separated by a disc which acts as a spacer and absorbs shock to the spine. This is surrounded by ligaments and muscles that support the lower back, in partnership with the abdominal muscles as well. Any of these structures could cause lower back pain and there is not always necessarily a specific cause. Lower back pain is one of the most common injuries reported by patients.
The term chronic implies a long-term injury, and so for the sake of this article it refers to any lower back pain that has lasted for three months or more.