Lower back pain affects approximately four out of five adults at least once during their lifetime, often inter-fering with work, recreation, or household chores and
other routine activities. It is one of the most common conditions for which Americans seek medical attention, and it is second only to headache as the most common neurological condition in the United States. According to the National Institute for Occupational Safety and Health, back pain related to work is one of the most-often diagnosed occupational disorders.
Health care dollars spent on the diagnosis and treatment of low back pain are estimated to be at least $50 billion annually, with additional costs related to disability and delay in return to work.
Back pain strikes equal numbers of men and women, and it typically begins between the fourth and sixth decades. The likelihood of disc disease and spinal degeneration, both prominent causes of back pain, increases with age. A sedentary lifestyle increases vulnerability to back pain, especially when coupled with obesity or sporadic bursts of overexertion.
Because of their greater flexibility and lack of agerelated degeneration, children and teenagers are much less prone than adults to develop medically significant back pain.
Causes and symptoms
The spinal column is composed of 24–25 movable bones, or vertebrae, held together by ligaments and separated by intervertebral discs that act as shock absorbers. Although this structure allows great flexibility and range of movement, it also affords many opportunities for injury. Compounding the potential for injury is that the human spine bears weight in the upright position and must therefore counteract gravity. Stresses on the muscles and ligaments that support the spine can cause acute pain or chronic injury.
With normal aging, the fluid cushioning the intervertebral discs tends to dry up, making them more brittle and less protective of the vertebrae. The normal wear and tear of daily activities can eventually erode the vertebral edges, undermining stability and putting pressure on nerves that enter and exit the spinal column to control movement and sensation of the arms and legs.
Heavy physical labor accelerates these processes, but lack of physical activity allows the muscles to lose tone, offering less protection to the spine as it twists and turns. Consequently, regardless of activity levels, back pain becomes more common with increasing age. Bone density and muscle flexibility and strength also tend to decrease with age, further increasing the chance of painful injury.
Obesity increases both the weight that the spine must support and the pressure on the discs, thereby elevating the risk of back pain and injury. Physically demanding sports can also damage the back, especially in the case of "weekend warriors" who overexert themselves on occasion while generally maintaining a low level of physical fitness. Even simple movements like bending over may trigger muscle spasms in individuals with chronic pain.
Injuries unrelated to activity may include motor vehicle accidents or falls that subject the spine and its supporting structures to direct impact or unusual torque. These injuries and those related to overexertion may result in painful sprain, strain, or spasm in the back muscles or ligaments.
Excessive strain or compression of the spine may cause disc herniation, in which the disc bulges or even ruptures. The bulging disc or its fragments may be displaced outward, putting pressure on nerve roots entering or exiting the spine and thereby causing pain. Most disc herniations occur in the lumbar or lower part of the spinal column, especially between the fourth and fifth lumbar vertebrae (L4 and L5, respectively) and between the fifth lumbar and first sacral vertebrae (L5 and S1, respectively).
Activities involving hyperextension of the back, such as gymnastics, may result in spondylosis, or disruption of the joint between adjacent vertebrae. A more extreme form of spondylosis is spondylolisthesis, or slippage of one vertebra relative to its neighbor. Impact or excessive mechanical force to the spine may cause spinal fracture. After repeated back injuries, buildup of scar tissue eventually weakens the back and can increase the risk of more serious injury.
Diseases of the bone, such as endocrine conditions or metastatic cancer spreading from the lung, breast, prostate, or other primary site, may cause fractures or other painful conditions in the spinal column. Fractures occurring without apparent traumatic injury, especially in a debilitated or chronically ill person, may be a warning of cancer or other underlying bone disease such as osteoporosis. Osteoporosis is a metabolic bone disease in which progressive decreases in bone strength and density makes the bones brittle, porous, and easily broken.
Other diseases causing back pain include arthritis, which erodes the joints, myopathies and inflammatory conditions, which involve the muscles, and neuropathy, which affects the nerves. Back pain is common in diabetes because this disease may be complicated by myopathy (though this is rare) or neuropathy, both of which create gait disturbances that, in turn, cause back pain. In women, fibromyalgia is a fairly common chronic condition associated with musculoskeletal pain, fatigue, morning stiffness, and other nonspecific symptoms.
Conditions affecting the spine include spinal degeneration from disc wear and tear, which can narrow the spinal canal and cause back stiffness and pain, especially upon awakening or after prolonged walking or standing. Spinal stenosis is a narrowing of the spinal canal, a condition that is present from birth. Both conditions increase the likelihood of back pain from disc disease. Spondylitis, or inflammation of the spinal joints, is characterized by chronic back pain and stiffness.
Anatomical abnormalities of the skeleton subject the vertebrae and supporting structures to increased strain, and often manifest as back pain. Scoliosis is an asymmetric curvature of the spine to one side. Kyphosis, or dowager's hump, refers to a pronounced rounding of the normal forward curve of the upper back, whereas lordosis (swayback) is an exaggeration of the normal backward arch in the lower back.
Lifestyle and general medical factors contributing to back pain include smoking, pregnancy, inherited disorders affecting the spine or limbs, poor posture, inappropriate posture for the activity being performed, and poor sleeping position. Psychological stress is a common but often unrecognized source of back pain. Injuries, arthritis, or other conditions affecting the feet, ankles, knees, or hips may result in abnormal walking patterns that exacerbate or cause back pain.
Apart from all the musculoskeletal structures and nerves, the internal organs can also be a source of pain felt in the back. Kidney stones, urinary tract infections, blood clots, stomach ulcers, and diseases of the pancreas can all be experienced as back pain. Fever or other bodily symptoms suggesting infection or involvement of internal organs should prompt a medical evaluation.
The discomfort of back pain may range from the dull ache of muscle soreness, to shooting or stabbing pain if a muscle acutely goes into spasm, to a toothache-like sensation along the course of a spinal nerve. Surprisingly, the severity of the pain may not be correlated with the severity of injury. In uncomplicated back strain, acute muscle spasm can cause agonizing back pain that prevents the person from standing up straight. On the other hand, a massive disc herniation may not produce pain or any other symptoms.
Depending on its source, back pain is usually aggravated by certain movements, although prolonged sitting or standing may also make it worse. Associated symptoms may include limited flexibility and range of motion, difficulty straightening up, or weakness in the arms or legs.
When back pain is caused by nerve compression, pain may travel, or radiate, from the back to peripheral areas, usually following the course of the nerve as it supplies the arm or leg. There may be numbness, sensitivity to touch, or "pins and needles" (tingling sensations) along the same distribution. Pain originating from an internal organ may also radiate to an area of the back supplied by the same nerve root as that organ.
Sciatica is a common form of nerve pain related to compression of fibers from one or more of the lower spinal nerve roots, characterized by burning low back pain radiating to the buttock and back of the leg to below the knee or even to the foot. In more severe cases, there may be numbness or tingling in the same regions, as well as weakness. Typically, sciatic pain is caused by a herniated or ruptured disc, but it may also rarely be caused by a tumor or cyst.
Worrisome symptoms associated with back pain that warrant immediate medical attention include loss of control of bowel or bladder, change in bowel and bladder habits, or profound or progressive weakness or sensory loss. Any of these may signal compression of one or more nerve roots, or even of the spinal cord itself, which may result in irreversible paralysis if not treated promptly.
Low back pain is unusual in children, unless caused by motor vehicle accidents and other traumatic injuries. One notable exception is back strain and muscle fatigue caused by carrying an overloaded backpack. According to the U.S. Consumer Product Safety Commission, more than 13,260 injuries caused by backpacks were treated at medical offices, clinics, and emergency rooms in 2000.
Persistent back pain in a young child should raise suspicions of a serious problem such as a tumor or infection of the spine, meriting further evaluation and treatment. Teenagers indulging in extreme sports may subject themselves to compression fractures, stress injuries, spondylosis, and rarely, disc herniation.
Laurie Barclay, The Gale Group Inc., Gale, Detroit,