Sciatica is the term applied to symptoms that develop due to irritation of the sciatic nerve. The sciatic nerves arise initially as a group of smaller nerves that branch off from the spinal cord on both sides of the lower lumbar and sacral area. This group of smaller nerves comes together in the pelvis as the sciatic nerve which then runs down each leg towards the foot, dividing into two parts in the lower leg.

The most common cause of sciatic nerve irritation is from a disc bulge or herniation in the lower spine. A bulging disc can put direct pressure on one or more of the component nerves where they branch off from the spinal cord. In addition, a disc injury will often produce inflammation and swelling, which can further compress and irritate the component nerves and the symptoms may be felt part or all of the way down the course of the sciatic nerve, starting in the buttock area and running down the leg to the foot.

Other sources of sciatica include bone spurs and direct trauma to the nerve itself, such as with an impact or heavy pressure applied just behind the hip joint. In rare occasions, a spinal tumor can compress the components of the sciatic nerve in the spinal canals, and in a few cases, a cyst or tumor may compress the sciatic nerve at the knee.

Although a commonly held misconception, not all leg pain is sciatica. True sciatica is typically described as being mostly in the back part of the leg, and may be described as a sharp or shooting pain, burning, tingling, or like an electric shock. Even when symptoms do meet that description it is not a sure indicator of true sciatica. In certain instances, knots of contraction called trigger points in a muscle called the piriformis that is located in the buttock area can cause referred pain that closely mimics and can be mistaken for sciatica. This is sometimes called "pseudo-sciatica". Trigger points in other muscles in the buttocks and upper thigh may produce referred pain on the outside of the leg that could be mistaken for sciatica as well.

In cases of true sciatica, there are various treatment options, most of which are directed at either treating a bulging disc and/or reducing inflammation to reduce pressure on the nerve. Although most cases of sciatica will resolve over time with or without treatment, due to the severity of the pain typically involved, most people with sciatica will seek out treatment. Unfortunately, many of the commonly-used treatments for sciatica have had very limited success, but new treatment options are becoming available that provide safer and more effective relief of sciatica symptoms