It is important to understand the cause of your spinal stenosis because that influences your diagnosis and treatment options. In general, the cause of spinal stenosis can be categorized as either primary or acquired.
Primary means your spinal stenosis may be congenital—you’ve had it since birth. It is not common. Some people are born with a spinal canal that is narrower than normal (see illustration below). This is a form of an inherited spinal stenosis called short pedicle syndrome. The signs or symptoms of primary spinal stenosis may not become apparent until adulthood; during mid-life years.
Acquired spinal stenosis develops as a result of disease (eg, degenerative disc disease) or injury.
Causes of Acquired Spinal Stenosis
The leading cause of acquired spinal stenosis is wear and tear on the spine due to aging. In fact, the most common direct cause of spinal stenosis is osteoarthritis, where the cartilage that cushions joints starts to degenerate due to age.
In young people, cartilage is smooth. As you grow older, the cartilage may become rough or may wear through completely, allowing bones to rub against each other. The body reacts to this rubbing by producing small bone growths called bone spurs (osteophytes). That's an effort to limit movement and therefore limit pain from the bones rubbing together.
That's relatively true: If you were to move less, your pain would mostly likely be less. However, you can't stop moving entirely, and less movement also reduces your quality of life. Plus, these bone spurs can create another kind of pain. In the spine, they can narrow the spinal canal (that's spinal stenosis), which may then compress your spinal cord or nerve roots.
In addition to osteoarthritis, you can also develop spinal stenosis from intervertebral disc problems. The intervertebral discs can bulge, or they can be ruptured or torn (a herniated disc). A bulging disc or fragments from a herniated disc can then protrude into the spinal canal or pinch on the nerve extending through the foramen. Ligaments connecting the vertebrae may also degenerate and allow the vertebrae to shift, which can pinch the spinal cord or nerves.
Risk factors for both osteoarthritis of the spine and for disc problems include aging, poor posture, high impact sports, and being overweight.
Injury to the spine can also cause spinal stenosis. For example, you may lift a heavy object without using proper lifting techniques. This can damage a disc or even move the vertebrae out of their normal alignment. Such injuries will put pressure on the spinal cord and nerve roots. You may also fracture part of your spine, and the fragments of bone can intrude on the spinal canal.
Any injury to the spine can also cause tissue swelling that puts pressure on the spinal cord or nerve roots, leading to spinal stenosis and back pain or neck pain.