When discussing sciatica it is important to understand the underlying medical cause of the sciatica symptoms in order to find effective treatment.
6 Most Common Causes of Sciatica
There are 6 lower back problems that are the most common causes of sciatica:
Lumbar herniated disc
A herniated disc occurs when the soft inner core of the disc (nucleus pulposus) leaks out, or herniates, through the fibrous outer core (annulus) and irritates the contiguous nerve root.
A herniated disc is sometimes referred to as a slipped disc, ruptured disc, bulging disc, protruding disc, or a pinched nerve. Sciatica is the most common symptom of a lumbar herniated disc.
Degenerative disc disease
While disc degeneration is a natural process that occurs with aging, for some people one or more degenerated discs in the lower back can also irritate a nerve root and cause sciatica.
Degenerative disc disease is diagnosed when a weakened disc results in excessive micro-motion at that spinal level, and inflammatory proteins from inside the disc become exposed and irritate the area (including the nerve roots).
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This condition occurs when a small stress fracture allows one vertebral body to slip forward on another (e.g. the L5 vertebra slips over the S1 vertebra).
With a combination of disc space collapse, the fracture, and the vertebral body slipping forward, the nerve can get pinched and cause sciatica.
Lumbar spinal stenosis
This condition commonly causes sciatica due to a narrowing of the spinal canal. Lumbar spinal stenosis is related to natural aging in the spine and is relatively common in adults over age 60.
The condition typically results from a combination of one or more of the following: enlarged facet joints, overgrowth of soft tissue, and a bulging disc placing pressure on the nerve roots, causing sciatica pain.
The sciatic nerve can get irritated as it runs under the piriformis muscle in the buttock. If the piriformis muscle irritates or pinches a nerve root that comprises the sciatic nerve, it can cause sciatica-type pain.
This is not a true radiculopathy (the clinical definition of sciatica), but the leg pain can feel the same as sciatica caused by a nerve irritation.
Sacroiliac joint dysfunction
Irritation of the sacroiliac joint - located at the bottom of the spine - can also irritate the L5 nerve, which lies on top of the sacroiliac joint, causing sciatica-type pain.
The leg pain can feel the same as sciatica caused by a nerve irritation.
More Causes of Sciatica
In addition to the most common causes, a number of other conditions can cause sciatica, including:
- Pregnancy. The changes that the body goes through during pregnancy, including weight gain, a shift on one's center of gravity, and hormonal changes, can cause sciatica during pregnancy.
- Scar tissue. If scar tissue compresses the nerve root, it can cause sciatica.
- Muscle strain. In some cases, inflammation related to a muscle strain can put pressure on a nerve root and cause sciatica.
- Spinal tumor. In rare cases, a spinal tumor can impinge on a nerve root in the lower back and cause sciatica symptoms.
- Infection. While rare, an infection that occurs in the low back can affect the nerve root and cause sciatica.
It is important to know the underlying clinical diagnosis of the cause of sciatica, as treatments will often differ depending on the cause.
For example, specific sciatica exercises, which are almost always a part of a treatment program, will be different depending on the underlying cause of the symptoms.