Lumbar stenosis refers to any narrowing of the spinal canal, which is the tube in the spinal column that carries the nerve roots. The most common form is degenerative, occurring in essentially the entire population with age, but to varying degrees and with varying clinical significance. This degenerative narrowing is referred to as spondylosis. Again, spondylolisthesis can have many causes, the most common being the degeneration affecting the intervertebral disc and facet joints between adjacent vertebrae.
Several factors contribute to the narrowing of the spinal canal with degenerative changes.
This may be analogous to degeneration and swelling of other joints in the body such as fingers. Secondly, the major ligament of the spinal canal, the ligamentum flavum, undergoes thickening and buckling. Fourth, as mentioned above, the vertebrae may slip forward. Finally, these changes may be superimposed on a congenitally narrow canal. These different causes, although individually minor, may combine to create a significant narrowing of the spinal canal.