According to the American Academy of Orthopedic Surgeons, acute back pain usually is caused by straining muscles that parallel the spine. When these muscles become weak due to lack of exercise, often by sitting too long on the job, or have been overworked in sporting activities or heavy lifting, they can spasm and knot up instead of contracting and relaxing as the back moves. Weak or stiff muscles can be sprained when the back twists or bends with sudden force, producing small muscle tears and painful inflammation. These injuries, which go by names like acute lumbosacral strain, mechanical back pain, and lumbago, usually heal within a few days to a few weeks. Doctors once suggested rest to heal such muscular problems, but recent studies have demonstrated that a speedier recovery is achieved by getting out of bed, in part because active muscles mend faster.
Exercise can strengthen and stretch out weak and tight muscles.
More challenging is chronic back pain, in which non-muscular back structures are usually the culprit. Diagnosing the source of any problem begins with a thorough history and physical exam. Sometimes a patient may also need a discogram, an uncomfortable procedure in which dye is injected into a suspect disc to raise pressure within it. Doctors know which particular disc is the cause of the problem if the injection recreates the patient's exact pain. Those suffering from chronic back pain could have a condition called spinal stenosis, a narrowing of the central canal through which the nerves of the spinal cord travel.