pain along the sciatic nerve, which runs from the lower back down the legs. Sciatica often develops following an unusual movement or exertion that places a strain on the lumbar portion of the spine (vertebral column), where the nerve has its roots, either immediately or after an interval of several hours to a few days. Researchers have identified a genetic mutation that significantly increases the risk of the condition. The pain of sciatica may become more severe with coughing (cough), sneezing, and flexion of the neck. It is relieved by positions that minimize traction on the sciatic nerve; for this reason, a person with sciatica tends to walk with the affected leg bent at the knee and externally rotated at the hip.

Sciatica is commonly associated with the rupture of a portion of an intervertebral disk into the spinal canal. It may also develop as a symptom of some local compressive lesion, or it may indicate a more generalized disorder involving the peripheral nerves. Most cases, including those in which the nerve is displaced by a protruding disk, can be treated effectively by bedrest on a firm mattress for several days to a few weeks. In some instances, however, surgical decompression of the nerve is necessary in order to prevent repeated attacks of disabling pain or to relieve weakness and sensory loss in the leg.