A herniated disk, complications of osteoarthritis, injuries, or narrowing of the spinal canal can cause sciatica.
Sciatica can cause intense pain that is felt from the low back, through the buttock, and down the back of either leg.
The diagnosis is based on a doctor's evaluation and sometimes on the results of imaging or electrodiagnostic tests.
Treatment includes measures to relieve pain and sometimes surgery.
The two sciatic nerves are the widest and longest nerves in the body. They are made up of several spinal nerve roots that come out of the spinal cord in the low back. Each sciatic nerve is almost as wide as a finger. On each side of the body, the sciatic nerve runs from the lower spine, behind the hip joint, down the buttock and leg to the back of the knee. There the sciatic nerve divides into several branches and continues to the foot.
When the sciatic nerve or the spinal nerve roots that make up the sciatic nerve are compressed, pinched, inflamed, or damaged, pain—sciatica—may radiate along the length of the sciatic nerve to the foot (see also Compression of the Spinal Cord). Sciatica occurs in about 5% of people who have low back pain.
In some people, no cause can be detected. In others, the cause may be a herniated disk, irregular projections of bone due to osteoarthritis, narrowing of the spinal canal (spinal stenosis), or swelling due to a sprained ligament. Rarely, Paget disease of bone, nerve damage due to diabetes (diabetic neuropathy), a spinal tumor, or an accumulation of blood (hematoma) or pus (abscess) pressing on the nerve causes sciatica. Some people seem to be prone to sciatica.
Sciatica usually affects only one side. The pain is felt from the low back, through the buttock, and down the back of either leg. The pain is typically burning, shooting, or stabbing. Pain that starts in one place but travels to another, usually along the path of a nerve, is called radiating pain.
Sciatica may cause a pins-and-needles sensation, a nagging ache, or shooting pain down the path of the nerve. Numbness or weakness may be felt in the leg or foot. Walking, running, climbing stairs, straightening the leg, and sometimes coughing or straining worsens the pain, which is relieved by straightening the back or standing.
If the cauda equina (the bundle of nerves extending from the bottom of the cord in the lower back) is affected, control of bladder and bowels can be lost. If these serious symptoms develop, medical attention is required immediately.
Doctors typically make the diagnosis of sciatica based on the characteristic pain. During a physical examination, doctors check a person's strength and reflexes.
Doctors may do other tests if people have weakness or numbness or if their symptoms have lasted for more than 6 weeks. Magnetic resonance imaging (MRI) and computed tomography (CT) are imaging tests that can help doctors identify abnormalities of the spine that are causing sciatica. Tests of the nerves and muscles (electrodiagnostic tests), such as nerve conduction studies and electromyography, can help doctors identify the affected spinal nerve root and the severity of the damage.
It is not always possible to prevent sciatica, but people can reduce their risk of developing it by
Regular exercise is an effective way to reduce the risk of developing sciatica. Aerobic exercise and specific muscle-strengthening and stretching exercises can help.
Aerobic exercise, such as swimming and walking, improves general fitness and generally strengthens muscles.
Specific exercises to strengthen and stretch the muscles in the abdomen, buttocks, and back (core muscles) can help stabilize the spine and decrease strain on the disks that cushion the spine and the ligaments that hold it in place.
Muscle-strengthening exercises include pelvic tilts and abdominal curls. Stretching exercises include the knee-to-chest stretch. Stretching exercises can increase back pain in some people and therefore should be done carefully. As a general rule, any exercise that causes or increases back pain should be stopped. Exercises should be repeated until the muscles feel mildly but not completely fatigued. Breathing during each exercise is important. People who have back pain should consult a doctor before beginning to exercise.
Exercises to Prevent Low Back Pain
Exercise can also help people maintain a desirable weight because being overweight increases the risk.
Maintaining good posture when standing, sitting, and sleeping reduces stress on the back. Slouching should be avoided. Chair seats can be adjusted to a height that allows the feet to be flat on the floor, with the knees bent up slightly and the lower back flat against the back of the chair. If a chair does not support the lower back, a pillow can be used behind the lower back. Sitting with the feet on the floor rather than with the legs crossed is advised. People should avoid standing or sitting for long periods. If prolonged standing or sitting is unavoidable, changing positions frequently may reduce stress on the back.
Learning to lift correctly helps prevent back injury. The hips should be aligned with the shoulders (that is, not rotated to one side or the other). People should not bend over with their legs nearly straight and reach out with their arms to pick up an object. Instead, they should bend at the hips and knees. Bending this way keeps the back straighter and brings the arms down to the object with the elbows at the side. Then, keeping the object close to the body, they lift the object by straightening their legs. This way, the legs, not the back, lift the object. Lifting an object over the head or twisting while lifting increases the risk of back injury.
Often, the pain goes away on its own. If it does not, people can try several methods of pain relief or may require surgery. Stretching the hamstring muscles gently after warming up may help.
One to two days of bed rest may provide pain relief. Longer bed rest weakens the core muscles and increases stiffness, thus worsening back pain and prolonging recovery. For many people, sleeping on their side with the knees bent and a pillow between the knees provides relief. People who sleep on their back can place a pillow under their knees. People can continue to sleep on their stomach if they are comfortable doing so.
Applying cold (such as ice packs) or heat (such as a heating pad) or using over-the-counter analgesics (such as acetaminophen and nonsteroidal anti-inflammatory drugs [NSAIDs]) may help relieve the pain. Some people may be helped by drugs that reduce nerve pain, such as gabapentin, antiseizure drugs, or certain antidepressants. If pain is severe or persists, doctors may give corticosteroids taken by mouth or injected into the epidural space (between the spine and the outer layer of tissue covering the spinal cord).
If a herniated disk is causing relentless or chronic sciatica, especially if accompanied by weakness and/or loss of sensation, surgical removal of the bulging part of the disk (diskectomy) and sometimes part of the vertebra (laminectomy) may be necessary. A general anesthetic is usually required. The hospital stay is usually 1 or 2 days. Often, microsurgical techniques, with a small incision and regional spinal anesthesia (which numbs only a specific part of the body), can be used to remove the herniated portion of the disk. Hospitalization for this procedure is usually not required. After either procedure, most people can resume all of their activities in 6 weeks to 3 months. Surgery tends to result in faster recovery than treatment without surgery. However, after about a year or two, people treated with and without surgery have about the same degree of recovery.