Sciatica: Encyclopedia II - Sciatica - Causes of sciatica

Sciatica - Causes of sciatica

Sciatica is generally caused by compression of the sciatic nerve. It is sometimes divided into two main categories. "True" sciatica is caused by compression at the nerve root from a "slipped disc" (a herniated disc in the spine), roughening and enlarging and/or misalignment of the vertebrae. "Pseudo-sciatica" is caused by compression of more peripheral sections of the nerve, usually from soft tissue tension in the piriformis or other related muscles. Unhealthy postural habits such as excessive sitting in chairs and sleeping in the fetal position, along with insufficient stretching and exercise of the relevant myofascial areas, can lead to both the vertebral and soft tissue problems associated with sciatica.

Other causes of sciatica include infections and tumors.

Sciatica may also be experienced in late pregnancy either as the result of the uterus pressing on the sciatic nerve, or secondarily from muscular tension or vertebral compression associated with the extra weight and postural changes inherent in pregnancy.

Pelvic entrapment of the sciatic nerve can also generate symptoms resembling spinal compression of the nerves. The most predominant form of this condition is known as piriformis syndrome. With this condition the piriformis muscle, which is located beneath the gluteal muscles, contracts in spasm and strangles the sciatic nerve, which is located beneath the muscle.

Yet another source of sciatica symptoms is caused by active trigger points in the lower back or gluteal muscles. In this case, the referred pain is not, in fact, coming from compression of the sciatic nerve, though the pain distribution down the buttocks and leg can be quite similar. Trigger points occur when muscles become ischemic (low blood flow) due to injury or chronic muscular contraction. The muscles most commonly associated with trigger points causing sciatica symptoms are the quadratus lumborum, the gluteus medius and minimus, and the deep hip rotators.

Adapted from the Wikipedia article "Causes of sciatica", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki