Sciatica is not a disease or a condition, but rather a symptom of some other underlying problem. The sciatic nerve is the longest nerve in the human body and, when damaged or compressed, can lead to sciatica. The main symptom of the condition is a sharp, shooting pain anywhere along the nerve, which runs from the lower back, through the buttocks, and down the back of either the right or left leg. People with sciatica may also experience a pins and needles sensation in the feet and toes.
A bulging or herniated disc is the most common cause of sciatica. Discs are spongy material found in between each vertebra. When a disc bulges or herniates, that spongy material protrudes backward and can irritate or even compress the nerve root. This compression and irritation cause sciatica. While most cases can and do improve on their own in time, many disc herniations can require surgery to alleviate the pain and risk of further damage.
Spinal stenosis is a narrowing in the spinal canal, which the bones in the spine form to protect the spinal cord. When this area narrows, it compresses the sciatic nerve, resulting in sciatica. Causes of spinal stenosis include an overgrowth of bone due to damage from osteoarthritis, thickened ligaments that bulge into the spinal canal, and spinal injuries that lead to dislocation or fracture of the bone, which then narrows the space.
Spondylolisthesis occurs when one of the vertebrae slips out of position and essentially dislocates. Stress fractures in the pars articularis portion of the vertebrae can cause this, as can degenerative spinal wear and tear, abnormal spine development, and erosion or damage from tumors, bone conditions, or previous spinal surgery. With this slippage, sciatica pain may come and go based on one's physical position. As the vertebrae move, they compress the sciatic nerve, but when the vertebrae move back, compression releases.
Paget’s disease is a rare chronic bone disorder that typically affects older individuals. It causes rapid and irregular bone growth and repair, often in the lower back. As the bones grow larger than they should, their increased size puts pressure on the sciatic nerve. The disease can also cause bone weakness, resulting in a weaker spinal structure and narrowing or pressure on the sciatic nerve.
Piriformis syndrome is a rare neuromuscular condition that affects the piriformis muscle in the buttocks. When the muscle becomes irritated, it compresses or irritates the sciatic nerve. Causes include trauma to the hip or buttocks, sitting for a long period, and genetic defects.
Abnormal growths or tumors can form inside the spinal cord or between the cord and vertebrae. Tumors in these areas are uncommon but spinal imaging such as MRI or CT scans can reveal them. The growth can place pressure on the sciatic nerve, resulting in sciatica.
Ankylosing spondylitis or AS is an autoimmune inflammatory arthritis that affects the vertebrae in the spine. In the early stages, people experience pain in the lower back and hips, but as the disease progresses, the vertebrae begin to fuse. This reduces the range of motion, and the excess bone growths can narrow the spinal column, placing pressure on the sciatic nerve.
Accidents or injuries involving the spine, such as automobile accidents, falls or crush injuries can cause breaks and other damage. Broken vertebrae can fragment, leaving small pieces in the spinal canal that put pressure on the sciatic nerve. As spinal injuries heal, overgrowth of bones can occur, narrowing the spinal space and placing pressure on the nerves.
Certain factors can increase the chance of sciatica. As we age, our bones repair more slowly, and changes in the spine occur. This can increase the risk of sciatica. Being overweight or obese can put increased stress on the spine and is another risk factor. People with diabetes are at increased risk of nerve damage related to sciatica.
Genetics and health aren’t the only risk factors. Activity levels and daily actions can also increase the risk of sciatica. Jobs that require heavy lifting, regular twisting at the waist, or extensive driving -- such as a semi-truck driver -- can contribute to sciatica. People who live sedentary lifestyles and spend most of the day sitting are also at an increased risk.
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