"Harrison's Principles of Internal Medicine" notes that back pain is one of the most common problems that cause people to visit a doctor. Back pain that varies with posture or position is usually caused by different types of problems with the muscles and bones in the back. The most common of these problems is simple muscle strain, which typically improves without treatment within a week or two, but there are other causes as well.
Muscle Strain
There are a number of small muscles in the back that help to maintain posture and move the spine in multiple directions. Because these muscles are small, they are easily strained by things such as improper lifting or sudden movements. These strains are the most common cause of back pain. Back pain from muscle strains is typically exacerbated by things such as maintaining an upright posture or moving the spine in specific directions, and usually improves when lying down and relaxed. It responds well to conservative therapies such as heat, aspirin and bed rest, and usually goes away within a few weeks without further treatment, according to a March 2005 article in the journal "Muscle and Nerve."
Disc Damage
Damage to the discs in the spine, while not nearly as common a cause as muscle strain, still accounts for a significant fraction of back pain cases. Discs are sections of cartilage that separate the vertebrae of the spine to cushion them and stop them from rubbing together. The discs lose some of their elasticity with age and become more susceptible to damage. Nerves run between the vertebrae of the spine, and when the cartilage separating the vertebrae is damaged, the nerves can become inflamed, which causes back pain. Back pain from disc damage may be exacerbated by specific movements of the spine, but the pain typically does not worsen with upright posture. Pain with leg movement is a distinctive positional feature of back pain from disc damage. When a leg is moved up towards the stomach, it causes an "electric" pain in the back that shoots down the leg. Back pain from disc damage is a chronic condition, and the treatment for it remains controversial. Numerous surgical approaches have been tried, but it's not clear that the results are any better than more conservative treatments, notes the 2005 article in "Muscle and Nerve." Injections of anti-inflammatory medication into area around the discs provide relief for many patients, but the procedure usually needs to be repeated every 3 to 4 months.
Muscle Spasm
In addition to strains, the small muscles of the back can cause pain through spasms. The exact causes of these spasms are unclear, but they appear to be more common in individuals with previous spinal injuries, notes "Harrison's Principles of Internal Medicine." Muscle spasms in the back typically involve the muscles that maintain posture rather than those associated with movement, so the pain is usually exacerbated by maintaining certain postures rather than specific movements. Muscle spasms in the back are often a chronic condition, but fortunately they usually respond well to treatment with muscle relaxant medications, notes "Muscle and Nerve."
References
- "Harrison's Principles of Internal Medicine"; Dennis L. Kasper, et al. (eds.); 2005
- "Muscle and Nerve"; Evaluation and treatment of low back pain: An evidence-based approach to clincal care"; SJ Atlas and RA Nardin; March 2005
