Spinal stenosis—a narrowing of the spinal canal—typically affects people in their 50s and 60s. It is usually the result of degenerative changes in the spine, or it may develop as a complication of surgery, trauma to the spine or, in rare instances, involvement of the spine in Paget’s disease, a bone disorder.
As the body ages, gradual deterioration of the disks and facet joints in the spine causes the bones to rub together. This may eventually lead to the formation of overgrowths or bone spurs (osteophytes) at the facet joints as well as around the rims of the vertebrae.
Spinal stenosis can occur when these overgrowths of bone gradually narrow the spinal canal. Ligaments may thicken and cause narrowing of the spinal canal as well. The narrowing leads to symptoms as the spinal cord or cauda equina becomes compressed. Symptoms vary, ranging from vague numbness and weakness in the legs while standing and walking to severe pain and difficulties with bowel and bladder control.
Symptoms of spinal stenosis usually start slowly and are mild at first. The pain does not follow the distribution of specific nerves but rather seems to involve the buttocks, thighs, calves and, occasionally, the entire length of both legs.
The pain feels like cramping and may be associated with weakness, a “rubbery” feeling, numbness and a sensation of loss of power in the legs. The symptoms typically improve with sitting down or bending forward. As a result of this weakness, people are prone to falls. Because the nerves controlling the bladder emerge from the lower spine, spinal stenosis may also cause urinary incontinence.