Spinal stenosis—a narrowing of the spinal canal—is usually the result of degenerative changes in the spine, or it may develop as a complication of surgery, trauma to the spine, or involvement of the spine in Paget’s disease. It typically affects people in their 50s and 60s.
As the body ages, gradual deterioration of the disks and facet joints in the spine causes the bones to rub together. This increased friction may eventually lead to the formation of overgrowths or bone spurs (called osteophytes) at the facet joints and around the rims of the vertebrae.
Spinal stenosis can occur when these overgrowths of bone gradually narrow the central canal of the spine; ligaments may thicken and cause narrowing of the spinal canal as well. The narrowing leads to symptoms as the spinal cord or the cauda equina becomes compressed. Symptoms can 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. Central stenosis can cause back pain, but usually the pain radiates into both legs. 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. 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.