Back pain is pain felt in the back that usually originates from the muscles, nerves, bones, joints or other structures in the spine. Back pain may have a sudden onset or can be a chronic pain; it can be constant or intermittent, stay in one place or radiate to other areas. It may be a dull ache, or a sharp or piercing or burning sensation. The pain may radiate into the arms and hands as well as the legs or feet, and may include symptoms other than pain. These symptoms may include tingling, weakness or numbness.
Back pain is one of humanity's most frequent complaints. In the U.S., acute low back pain (also called lumbago) is the fifth most common reason for physician visits. About nine out of ten adults experience back pain at some point in their life, and five out of ten working adults have back pain every year. Low back pain causes 40% of missed days of work in the United States. Additionally, it is the single leading cause of disability worldwide.
The spine is a complex interconnecting network of nerves, joints, muscles, tendons and ligaments, all of which are capable of producing pain. Large nerves that originate in the spine and go to the legs and arms can make pain radiate to the extremities.
There are several potential sources and causes of back pain. However, the diagnosis of specific tissues of the spine as the cause of pain presents problems. This is because symptoms arising from different spinal tissues can feel very similar and is difficult to differentiate without the use of invasive diagnostic intervention procedures, such as local anesthetic blocks.
One potential source of back pain is skeletal muscle of the back. Potential causes of pain in muscle tissue include muscle strains (pulled muscles), muscle spasm, and muscle imbalances. However, imaging studies do not support the notion of muscle tissue damage in many back pain cases, and the neurophysiology of muscle spasm and muscle imbalances is not well understood.
Another potential source of lower back pain is the synovial joints of the spine (e.g. zygapophysial joints/facet joints. These have been identified as the primary source of the pain in approximately one third of people with chronic low back pain, and in most people with neck pain following whiplash. However, the cause of zygapophysial joint pain is not fully understood. Capsule tissue damage has been proposed in people with neck pain following whiplash. In people with spinal pain stemming from zygapophysial joints, one theory is that intra-articular tissue such as invaginations of their synovial membranes and fibro-adipose meniscoids (that usually act as a cushion to help the bones move over each other smoothly) may become displaced, pinched or trapped, and consequently give rise to nociception (pain).
There are several common other potential sources and causes of back pain: these include spinal disc herniation and degenerative disc disease or isthmic spondylolisthesis, osteoarthritis (degenerative joint disease) and lumbar spinal stenosis, trauma, cancer, infection, fractures, and inflammatory disease. The anterior ligaments of the intervertebral disc are extremely sensitive, and even the slightest injury can cause significant pain.
Radicular pain (sciatica) is distinguished from 'non-specific' back pain, and may be diagnosed without invasive diagnostic tests.
New attention has been focused on non-discogenic back pain, where patients have normal or near-normal MRI and CT scans. One of the newer investigations looks into the role of the dorsal ramus in patients that have no radiographic abnormalities. See Posterior Rami Syndrome.
In most cases of low back pain medical consensus advises not seeking an exact diagnosis but instead beginning to treat the pain. This assumes that there is no reason to expect that the person has an underlying problem. In most cases, the pain goes away naturally after a few weeks. Typical people who do seek diagnosis through imaging are not likely to have a better outcome than those who wait for the condition to resolve.
In cases in which the back pain has a persistent underlying cause, such as a specific disease or spinal abnormality, then it is necessary for the physician to differentiate the source of the pain and advise specific courses of treatment.