What is Sciatica?

Sciatica is a relatively common form of low back pain and leg pain. The true meaning of the term often is misunderstood. Sciatica is a set of symptoms rather than a diagnosis for what is irritation the root of the nerve, causing the pain. This point is important, because treatment for sciatica or sciatic symptoms will often be different, depending upon the underlying cause of the symptoms. The purpose of this article is to identify common causes of sciatica.

Sciatica is pain caused by general compression and/or irritation of one of five nerve roots that are branches of the sciatic nerve, and represents one of the most common forms of radiculopathy. Radiculopathy is not a specific condition, but rather a description of a problem in which on or more nerves are affected and do not work properly. This can result in pain (radicular pain, or radiculitis, which is pain “radiated” along the dermatome (sensory distribution) of a nerve due to inflammation or other irritation of the nerve root), weakness, numbness, or difficulty controlling specific muscles. The pain is typically felt in the lower back, buttock, and/or various parts of the leg and foot. Typically, the symptoms are only felt on one side of the body.

One cause of sciatica is a spinal disc herniation, pressing on one of the sciatic nerve roots. The spinal discs are composed of a spongiform cartilage with a liquid center. The discs separate the vertebrae, thereby allowing room for the nerve roots to properly exit through the spaces between the L4, L5 and sacral vertebrae. The discs cushion the spine from compressive forces, but are weak to pressure applied during rotational movements. That is why a person who bends to one side, at a bad angle, to pick up a piece of paper may more likely herniated a spinal disc than an person falling from a ladder and landing on his or her back. Herniation of a disc occurs when the liquid center of the disc bulges outwards, tearing the external ring of fibers, and compresses a nerve root against the lamina or pedicle of a vertebrae, thus causing sciatica.

Other compressive spinal causes include spinal canal stenosis, a condition wherein the spinal canal (the spaces though which the spinal cord runs) narrows and compresses the spinal cord. This narrowing can be caused by bone spurs, vertebral dislocation, inflammation, or herniated disc which decreases available space for the spinal cord, thus pinching nerves in the spinal cord that travel to the sciatic nerve and irritating them with friction.

The sciatic nerve runs through the piriformis muscle in the buttocks region beneath the gluteal muscles. When the muscle shortens or spasm due to trauma, it can compress or strangle the sciatic nerve beneath the muscle. This cause of sciatic symptoms is piriformis syndrome. This may be the major cause of sciatica when the nerve root is normal.

The risk of self-inflicted sciatica has increased in recent years with the fashion trend of lower-hanging trousers as well as lower-positioning of the pockets. For instance, sitting on a wallet for prolonged hours every day can cause self-inflicted sciatica. Symptoms of numbness and/or pain behind the knee cap are associated with this form of sciatica.

Another source of sciatica symptoms is active trigger points of the lower back and the gluteal muscles. In this case, the referred pain is not consequent to compression of the sciatic nerve, thought the pain distribution down the buttocks and leg is similar. Trigger points occurs when muscles become ischemic (low blood flow) due to injury or chronic muscular contraction. The most commonly associated muscles with trigger points triggering sciatic symptoms are: the quadratus lumborum, the gluteus medius, the gluteus minimus, and the deep hip rotator musculature.

Sciatica may also be experienced in late pregnancy, primarily resulting from the uterus pressing the sciatic nerve, and secondarily from the muscular tension and/or vertebral compression consequent to carrying the extra weight of the fetus, and the postural changes inherent to pregnancy.

The good news is that all of the aforementioned conditions are highly treatable and typically respond well to conservative measure. If you have any questions regarding this article you may contact Progressive Physical Therapy at (301) 729-3485.