Spinal stenosis, the narrowing of spaces within the spine, is a common issue affecting millions, particularly as they age. This constriction places pressure on the spinal cord and the nerves that branch out from it, leading to a range of symptoms. Accurately counting cases is challenging because prevalence estimates must separate anatomical degeneration from the number of people who seek medical treatment.
What Is Spinal Stenosis
Spinal stenosis is the narrowing of the spinal canal or the small openings between vertebrae, known as the neural foramen. This narrowing is most often acquired later in life due to degenerative changes, frequently driven by osteoarthritis. As cartilage breaks down, the body attempts to stabilize the spine by growing new bone, resulting in bone spurs (osteophytes) that project into the spinal canal.
Other common causes include the bulging or herniation of intervertebral discs and the thickening of ligaments, such as the ligamentum flavum. Most cases affect the lower back (lumbar spinal stenosis) or the neck (cervical spinal stenosis). When the space narrows, it compresses the spinal cord or nerve roots, causing symptoms like pain, numbness, tingling, and weakness that often radiate into the arms or legs.
Prevalence Rates and Demographics
Spinal stenosis is overwhelmingly a condition of aging, with prevalence increasing dramatically after age 50. It is a significant cause of disability in older individuals. The prevalence of symptomatic lumbar spinal stenosis (LSS) is estimated at approximately 11% in the general population.
In the United States, LSS affects more than 200,000 individuals and is the most common reason for spinal surgery among patients over age 65. Age-related data shows symptomatic LSS affects 1.9% of people aged 40 to 49, jumping to 10.8% in those aged 70 to 79. For those over 60, radiographic evidence of lumbar stenosis is present in 21% of individuals.
While LSS is the most common form, cervical stenosis is also prevalent. A fraction of those with severe symptoms proceed to surgery; laminectomy is the most frequent procedure. In the Medicare population, about 37% of patients with stenosis alone are managed operatively.
Challenges in Accurately Counting Cases
Variations in reported numbers for spinal stenosis stem from methodological difficulties and a lack of standardized diagnostic criteria. The primary challenge is distinguishing between anatomical stenosis and symptomatic stenosis. Radiological studies frequently show narrowing in people who experience no symptoms at all.
For instance, studies have found that while radiological evidence of LSS is observed in 20% of people over 60, 80% of these individuals are asymptomatic. Using imaging alone to count cases thus leads to a substantial overestimation of the population experiencing discomfort or disability.
Furthermore, the symptoms of spinal stenosis (low back pain, numbness, weakness) often overlap with other age-related spinal conditions. This overlap makes accurate attribution difficult, as pain may be due to disc degeneration rather than nerve compression caused by stenosis. Because studies rely on different diagnostic definitions—based on imaging, symptoms, or surgical intervention—the reported prevalence figures vary widely.