Anatomically, individual vertebra interconnect in several places, making canals and holes through which nerves and the spinal cord pass. In spinal stenosis, pressure is put on the nervous tissue that traverses these openings. This pressure causes pain. It can also cause neurological problems, such as muscle weakness, numbness, or even loss of bowel, bladder and sexual function.
Spinal stenosis might also be found along the spinal canal, which is the passageway through which the highly sensitive spinal cord passes.
While spinal stenosis can be caused by many things, most cases are due to aging and the related presence of osteoarthritis. When osteoarthritis of the spine develops to the point where the intervertebral disk has worn away and bone rubs against bone, the body attempts to remedy this painful condition by forming bone spurs. Depending upon their location, these bones spurs may compress the spinal cord and/or nerve roots.
Also, degenerative changes in spinal ligaments can lead to stenosis. Spinal ligaments stiffen and thicken over time in many people. This, in turn, compresses and shortens the spine. The compression will put pressure on the nerve roots, and will likely cause pain or neurological problems.
About 75% of spinal stenosis cases are lumbar spinal stenosis (LSS), in the lower back.