As people age, bone strength and muscle elasticity and tone tend to decrease. The discs begin to lose fluid and flexibility, which decreases their ability to cushion the vertebrae. Pain can occur when, for example, someone lifts something too heavy or overstretches, causing a sprain, strain, or spasm in one of the muscles or ligaments in the back. If the spine becomes overly strained or compressed, a disc may rupture or bulge outward. This rupture may put pressure on one of the more than 50 nerves rooted to the spinal cord that control body movements and transmit signals from the body to the brain. When these nerve roots become compressed or irritated, back pain results.
Low back pain may reflect nerve or muscle irritation or bone lesions. Most low back pain follows injury or trauma to the back, but pain may also be caused by degenerative conditions such as arthritis or disc disease, osteoporosis or other bone diseases, viral infections, irritation to joints and discs, or congenital abnormalities in the spine. Obesity, smoking, weight gain during pregnancy, stress, poor physical condition, posture inappropriate for the activity being performed, and poor sleeping position also may contribute to low back pain. Additionally, scar tissue created when the injured back heals itself does not have the strength or flexibility of normal tissue. Buildup of scar tissue from repeated injuries eventually weakens the back and can lead to more serious injury. Occasionally, low back pain may indicate a more serious medical problem. Pain accompanied by fever or loss of bowel or bladder control, pain when coughing, and progressive weakness in the legs may indicate a pinched nerve or other serious condition. People with diabetes may have severe back pain or pain radiating down the leg related to neuropathy. People with these symptoms should contact a doctor immediately to help prevent permanent damage.
Who is Most Likely to Develop Low Back Pain?
Nearly everyone has low back pain sometime. Men and women are equally affected. It occurs most often between ages 30 and 50, due in part to the aging process but also as a result of sedentary life styles with too little (sometimes punctuated by too much) exercise. The risk of experiencing low back pain from disc disease or spinal degeneration increases with age.
Low back pain unrelated to injury or other known cause is unusual in pre-teen children. However, a backpack overloaded with schoolbooks and supplies can quickly strain the back and cause muscle fatigue. The U.S. Consumer Product Safety Commission estimates that more than 13,260 injuries related to backpacks were treated at doctors’ offices, clinics, and emergency rooms in the year 2000. To avoid back strain, children carrying backpacks should bend both knees when lifting heavy packs, visit their locker or desk between classes to lighten loads or replace books, or purchase a backpack or airline tote on wheels.
Conditions That Are Associated with Low Back Pain
Conditions that may cause low back pain and require treatment by a physician or other health specialist include:
Bulging disc (also called protruding, herniated, or ruptured disc). The intervertebral discs are under constant pressure. As discs degenerate and weaken, cartilage can bulge or be pushed into the space containing the spinal cord or a nerve root, causing pain. Studies have shown that most herniated discs occur in the lower, lumbar portion of the spinal column. A much more serious complication of a ruptured disc is cauda equina syndrome, which occurs when disc material is pushed into the spinal canal and compresses the bundle of lumbar and sacral nerve roots. Permanent neurological damage may result if this syndrome is left untreated.
Sciatica is a condition in which a herniated or ruptured disc presses on the sciatic nerve, the large nerve that extends down the spinal column to its exit point in the pelvis and carries nerve fibers to the leg. This compression causes shock-like or burning low back pain combined with pain through the buttocks and down one leg to below the knee, occasionally reaching the foot. In the most extreme cases, when the nerve is pinched between the disc and an adjacent bone, the symptoms involve not pain but numbness and some loss of motor control over the leg due to interruption of nerve signaling. The condition may also be caused by a tumor, cyst, metastatic disease, or degeneration of the sciatic nerve root.
Spinal degeneration from disc wear and tear can lead to a narrowing of the spinal canal. A person with spinal degeneration may experience stiffness in the back upon awakening or may feel pain after walking or standing for a long time.
Spinal stenosis related to congenital narrowing of the bony canal predisposes some people to pain related to disc disease.
Osteoporosis is a metabolic bone disease marked by progressive decrease in bone density and strength. Fracture of brittle, porous bones in the spine and hips results when the body fails to produce new bone and/or absorbs too much existing bone. Women are four times more likely than men to develop osteoporosis. Caucasian women of northern European heritage are at the highest risk of developing the condition.
Skeletal irregularities produce strain on the vertebrae and supporting muscles, tendons, ligaments, and tissues supported by spinal column. These irregularities include scoliosis, a curving of the spine to the side; kyphosis, in which the normal curve of the upper back is severely rounded; lordosis, an abnormally accentuated arch in the lower back; back extension, a bending backward of the spine; and back flexion, in which the spine bends forward.
Fibromyalgia is a chronic disorder characterized by widespread musculoskeletal pain, fatigue, and multiple “tender points,” particularly in the neck, spine, shoulders, and hips. Additional symptoms may include sleep disturbances, morning stiffness, and anxiety.
Spondylitis refers to chronic back pain and stiffness caused by a severe infection to or inflammation of the spinal joints. Other painful inflammations in the lower back include osteomyelitis (infection in the bones of the spine) and sacroiliitis (inflammation in the sacroiliac joints).
How is Low Back Pain Diagnosed?
A thorough medical history and physical exam can usually identify any dangerous conditions or family history that may be associated with the pain. The patient describes the onset, site, and severity of the pain; duration of symptoms and any limitations in movement; and history of previous episodes or any health conditions that might be related to the pain. The physician will examine the back and conduct neurologic tests to determine the cause of pain and appropriate treatment. Blood tests may also be ordered. Imaging tests may be necessary to diagnose tumors or other possible sources of the pain.
A variety of diagnostic methods are available to confirm the cause of low back pain:
X-ray imaging includes conventional and enhanced methods that can help diagnose the cause and site of back pain. A conventional x-ray, often the first imaging technique used, looks for broken bones or an injured vertebra. A technician passes a concentrated beam of low-dose ionized radiation through the back and takes pictures that, within minutes, clearly show the bony structure and any vertebral misalignment or fractures. Tissue masses such as injured muscles and ligaments or painful conditions such as a bulging disc are not visible on conventional x-rays. This fast, noninvasive, painless procedure is usually performed in a doctor’s office or at a clinic.
Discography involves the injection of a special contrast dye into a spinal disc thought to be causing low back pain. The dye outlines the damaged areas on x-rays taken following the injection. This procedure is often suggested for patients who are considering lumbar surgery or whose pain has not responded to conventional treatments. Myelograms also enhance the diagnostic imaging of an x-ray. In this procedure, the contrast dye is injected into the spinal canal, allowing spinal cord and nerve compression caused by herniated discs or fractures to be seen on an x-ray.
Computerized tomography (CT) is a quick and painless process used when disc rupture, spinal stenosis, or damage to vertebrae is suspected as a cause of low back pain. X-rays are passed through the body at various angles and are detected by a computerized scanner to produce two-dimensional slices (1 mm each) of internal structures of the back. This diagnostic exam is generally conducted at an imaging center or hospital in Minneapolis.
Magnetic resonance imaging (MRI) is used to evaluate the lumbar region for bone degeneration or injury or disease in tissues and nerves, muscles, ligaments, and blood vessels. MRI scanning equipment creates a magnetic field around the body strong enough to temporarily realign water molecules in the tissues. Radio waves are then passed through the body to detect the “relaxation” of the molecules back to a random alignment and trigger a resonance signal at different angles within the body. A computer processes this resonance into either a three-dimensional picture or a two-dimensional “slice” of the tissue being scanned, and differentiates between bone, soft tissues and fluid-filled spaces by their water content and structural properties. This noninvasive procedure is often used to identify a condition requiring prompt surgical treatment.
Electrodiagnostic procedures include electromyography (EMG), nerve conduction studies, and evoked potential (EP) studies. EMG assesses the electrical activity in a nerve and can detect if muscle weakness results from injury or a problem with the nerves that control the muscles. Very fine needles are inserted in muscles to measure electrical activity transmitted from the brain or spinal cord to a particular area of the body. With nerve conduction studies the doctor uses two sets of electrodes (similar to those used during an electrocardiogram) that are placed on the skin over the muscles. The first set gives the patient a mild shock to stimulate the nerve that runs to a particular muscle. The second set of electrodes is used to make a recording of the nerve’s electrical signals, and from this information the doctor can determine if there is nerve damage. EP tests also involve two sets of electrodes – one set to stimulate a sensory nerve and the other set on the scalp to record the speed of nerve signal transmissions to the brain.
Bone scans are used to diagnose and monitor infection, fracture, or disorders in the bone. A small amount of radioactive material is injected into the bloodstream and will collect in the bones, particularly in areas with some abnormality. Scanner-generated images are sent to a computer to identify specific areas of irregular bone metabolism or abnormal blood flow, as well as to measure levels of joint disease.
Thermography involves the use of infrared sensing devices to measure small temperature changes between the two sides of the body or the temperature of a specific organ. Thermography may be used to detect the presence or absence of nerve root compression.
Ultrasound imaging, also called ultrasound scanning or sonography, uses high-frequency sound waves to obtain images inside the body. The sound wave echoes are recorded and displayed as a real-time visual image. Ultrasound imaging can show tears in
ligaments, muscles, tendons, and other soft tissue masses in