The longest nerve in your body, the sciatic nerve runs from your pelvis through your buttock and hip area and down the back of each leg. It controls many of the muscles in your lower legs and provides feeling to your thighs, legs and feet. The term "sciatica" refers to pain that radiates along the path of this nerve, from your back into your buttock and leg.

Sciatica isn't a disorder in and of itself. Instead, it's a symptom of another problem involving the nerve, such as a herniated disk. Pain that radiates from your lower (lumbar) spine to your buttock and down the back of your leg is the hallmark of sciatica. You may feel the discomfort almost anywhere along the nerve pathway, but it's especially likely to follow a path from your low back to your buttock and the back of your thigh and calf.

The pain can vary widely, from a mild ache to a sharp, burning sensation or excruciating discomfort. Sometimes it may feel like a jolt or electric shock. Sciatic pain often starts gradually and intensifies over time. It may be worse when you cough or sneeze, and prolonged sitting or walking can also aggravate symptoms. Usually only one lower extremity is affected.
In addition to pain, you may also experience:

  • Numbness or muscle weakness along the nerve pathway in your leg or foot. In some cases, you may have pain in one part of your leg and numbness in another.
  • Tingling or a pins-and-needles feeling, most commonly in your toes or part of your foot.
  • A loss of bladder or bowel control. This is a sign of cauda equina syndrome, a rare but serious condition that requires emergency care. If you experience either of these symptoms, seek medical help immediately.

Sciatica frequently occurs when a nerve root is compressed in your lower (lumbar) spine, most often as a result of a herniated disk in the low back. Disks are pads of cartilage that separate the bones (vertebrae) in your spine. They keep your spine flexible and act as shock absorbers to cushion the vertebrae when you move.

But as you grow older, the disks may start to deteriorate, becoming drier, flatter and more brittle. Eventually, the tough, fibrous outer covering of the disk may develop tiny tears, causing the jelly-like substance in the disk's center to seep out (herniation or rupture). The herniated disk may then press on a nerve root, causing pain in your back, leg or both. If the damaged disk is in the middle or lower part of your back, you also may experience numbness, tingling or weakness in your buttock, leg or foot.

Although a herniated disk is by far the most common cause of sciatic nerve pain, other conditions can also put pressure on the sciatic nerve, including:

  • Lumbar spinal stenosis. Your spinal cord is a bundle of nerves that extends the length of your spine. It's housed inside a channel (spinal canal) within the vertebrae. Thirty-one pairs of nerves branch off from the spinal cord, providing communication between your brain and the rest of your body. In spinal stenosis, one or more areas in the spinal canal narrow, putting pressure on the spinal cord or on the roots of the branching nerves. When the narrowing occurs in the lower spine, the lumbar and sacral nerve roots may be affected.

  • Spondylolisthesis. This condition, often the result of degenerative disk disease, occurs when one vertebra slips slightly forward over another vertebra. The displaced bone may pinch the sciatic nerve where it leaves the spine.

  • Piriformis syndrome. Running directly above the sciatic nerve, the piriformis muscle starts at your lower spine and connects to each thighbone (femur). Piriformis syndrome occurs when the muscle becomes tight or goes into spasms, putting pressure on the sciatic nerve. The pain may radiate down the back of your thigh but doesn't extend below the knee. Prolonged sitting, car accidents and falls also can contribute to piriformis syndrome.

  • Trauma. A car accident, fall or blow to the spine can injure the lumbar or sacral nerve roots. of which could potentially result in sciatic pain.

Risk factors are health problems, lifestyle choices and inherent qualities, such as age or race, that make it more likely you'll develop a particular condition. Major risk factors for sciatica include:

  • Age. Age-related changes in the spine are the most common cause of sciatica. You're likely to have some deterioration in the disks in your back by the time you're 30, and most people who develop herniated disks are in their 30s and 40s. Spinal stenosis, another leading cause of sciatica, primarily strikes people in their 50s and beyond.

  • Occupation. A job that requires you to twist your back, carry heavy loads or drive a motor vehicle for long periods makes you more prone to develop sciatica.

  • Physical activity. Although walking and jogging have been associated with an increased risk of sciatica, exercise in general has not. In fact, people who sit for prolonged periods or have a sedentary lifestyle are more likely to develop sciatica than active people are.

  • Genetic factors. Researchers have identified two genes that may predispose some people to disk problems.

  • Diabetes. This condition, which affects the way your body uses blood sugar, increases your risk of nerve damage.

To help diagnose sciatica and pinpoint any nerve entrapments your doctor will ask about your medical history and perform a thorough physical exam, paying special attention to your spine and legs. You will also have tests that check your muscle strength and reflexes. For example, you may be asked to walk on your toes or heels, rise from a squatting position and, while lying on your back, lift your legs one at a time straight in the air. Pain that results from sciatica will usually become worse during these activities.

If your pain lasts longer than six weeks or is very severe, you may have one or more imaging tests. These tests include:

  • Spinal X-ray. Because ordinary X-rays can't detect herniated disk problems or nerve damage, they're not usually helpful for pinpointing the cause of sciatica. A spinal X-ray can show most cancers affecting the bony structures of the spine, narrowed disks and spondylolisthesis, however, and can help rule out other causes of nerve root impingement.

  • Magnetic resonance imaging (MRI). This is probably the most sensitive test for assessing sciatic nerve pain. Instead of X-rays, MRI uses a powerful magnet and radio waves to produce cross-sectional images of your back. The test can detect damage to your disks and ligaments as well as the presence of tumors. MRI is noninvasive and has no harmful side effects. 

    During the test, you lie on a movable table inside the MRI machine, which is essentially a large magnet. Some MRI units may be wider, shorter or open on all sides, which may be more comfortable for you, although the quality of images taken with these systems may vary.

Even you are being treated by a chiropractor you'll heal more quickly if you continue with your usual activities but avoid what may have triggered the pain in the first place. Although resting for a day or so may provide some relief, prolonged bed rest isn't a good idea. In the long run, inactivity will make your symptoms worse.
In addition, try the following measures:

  • Cold packs. Initially, your doctor may suggest using cold packs to reduce inflammation and relieve discomfort. Wrap an ice pack or a package of frozen peas in a clean towel and apply to the painful areas for 15 to 20 minutes at least four times a day.

  • Stretching. Initially, passive stretching exercises for your low back can help you feel better and may help relieve nerve root compression, but avoid jerking, bouncing or twisting. Avoid overstretching your painful muscles. This can cause increased pressure on the sciatic nerve during the initial phase of injury and inflammation.

  • Rehabilitation can play a vital role in your recovery. Once acute pain improves, your doctor or a physical therapist can design a rehabilitation program to help prevent recurrent injuries.

  • Rehabilitation typically includes exercises to help correct your posture, strengthen the muscles supporting your back and improve your flexibility. Your doctor will have you start your correctiv exercise program both as early as possible. A Corrective Exercise Specialist can assess your movement patterns and determine any muscular or skeletal imbalances contributed to your sciatic nerve condition. This professional can create and design a rehab program that is specific to your imbalances and how to correct them.

  • Regular exercise. It may seem counterintuitive to exercise when you're in pain, but regular exercise is one of the best ways to combat chronic discomfort.

  • Exercise prompts your body to release endorphins — chemicals that prevent pain signals from reaching your brain. Endorphins also help alleviate anxiety and depression, conditions that can make your pain more difficult to control. What's more, combining aerobics with strength training and exercises that maintain or improve flexibility can help prevent age-related degenerative changes in your back.

    If you're new to exercise, it is important that you ask for guidance from a trained professional as you progress into exercise.

It's not always possible to prevent sciatica, but the following suggestions can play a key role in protecting your back:

  • Exercise regularly. This is the most important thing you can do for your overall health as well as for your back. Pay special attention to your core muscles — the muscles in your abdomen and lower back that are essential for proper posture and alignment. Pilates — an exercise technique for total body conditioning and rehabilitation — may be particularly helpful in keeping these muscles strong. For cardiovascular benefits, try using a stationary bike, treadmill, elliptical trainer or cross-country ski machine. Cycling outdoors is also recommended, but be sure your seat and handlebars are adjusted properly.

  • Maintain proper posture when you sit. A good chair should comfortably support your hips and the seat shouldn't press on the back of your thighs or knees. If the chair doesn't support the natural curve in your lower spine, place a rolled towel or pillow behind your back.
    When working at a computer, adjust your chair so that your feet are flat on the floor and your arms rest on your desk or the chair's arms, with your elbows bent at a right angle. Take frequent breaks, even if it's just to walk around your office.

    When you drive, adjust your seat to keep your knees and hips level, and move the seat forward to avoid overreaching for the pedals.

  • Use good body mechanics. Being conscious of how you stand, lift heavy objects and even how you sleep can go a long way toward keeping your back healthy. That's because poor posture stresses your back, leading to fatigue and stress on joints and nerves. If you stand for long periods, rest one foot on a stool or small box from time to time. While you stand, hold reading material at eye level instead of bending forward.

    Before you lift something heavy, decide where you'll place it and how you'll get there. Bend at your knees, not your back, so that your legs do the lifting. Carry objects close to your body at about waist level. If possible, set the object down on a surface between shoulder and knee height to avoid lifting objects over your head or bending over too far. Don't twist at your waist. Instead, turn by pivoting your feet.

    Be careful moving heavy things when you're tired — fatigue can cause you to move more awkwardly. Heavy loads pose the greatest risk, so know your limitations. Don't attempt to lift something you feel is beyond your ability.

For the best sleep posture, choose a firm mattress. Use pillows for support, but don't use one that forces your neck up at a severe angle.