Spinal stenosis is caused by the physical narrowing of the spinal canal. This spine condition occurs when the combination of disc degeneration and facet arthritis narrow the spinal canal or openings (foramen) for the exiting nerve roots enough to irritate or compress the nerves.
Typically, the nerves are caught between the disc annulus in the front and expanded facets on the back side of the spinal canal. When the disc loses height, the surrounding annulus bulges back into the canal, much like a tire without sufficient air pressure.
The arthritic facet joint capsules thicken due to chronic inflammation. Facet osteophytes grow ever larger in their attempt to stabilize the spine. The space left for the nerves continues to get smaller. If this occurs gradually, the nerves can accommodate to a surprising extent. However, eventually the space gets so small that normal nerve function is no longer possible.
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