What it is
Spinal stenosis occurs when the space around the spinal cord narrows. This puts pressure on the spinal cord and the spinal nerve roots, and may cause pain, numbness, or weakness in the legs.
As we age, the bone in our spines may harden and become overgrown. This can lead to a narrowing of the spinal canal, called stenosis.
When stenosis occurs in the lower back, it is called lumbar spinal stenosis. It often results from the normal aging process. As people age, the soft tissues and bones in the spine may harden or become overgrown. These degenerative changes may narrow the space around the spinal cord and result in spinal stenosis.
Degenerative changes of the spine are seen in up to 95% of people by the age of 50. Spinal stenosis most often occurs in adults over 60 years old. Pressure on the spinal cord is equally common in men and women, although women are more likely to have symptoms that require treatment.
A small number of people are born with back problems that develop into lumbar spinal stenosis. This is known as congenital spinal stenosis. It occurs most often in men. People usually first notice symptoms between the ages of 30 and 50.
Arthritis is the most common cause of spinal stenosis. Arthritis is the degeneration of any joint in the body.
In the spine, arthritis can result as the disk degenerates and loses water content. In children and young adults, disks have high water content. As we get older, our disks begin to dry out and weaken. This problem causes settling, or collapse, of the disk spaces and loss of disk space height.
As the spine settles, two things occur. First, weight is transferred to the facet joints behind the spinal cord. Second, the tunnels that the nerves exit through become smaller.
As the facet joints experience increased pressure, they also begin to degenerate and develop arthritis, similar to the hip or knee joint. The cartilage that covers and protects the joints wears away. If the cartilage wears away completely, it can result in bone rubbing on bone. To make up for the lost cartilage, your body may respond by growing new bone in your facet joints to help support the vertebrae. Over time, this bone overgrowth-called spurs-may narrow the space for the nerves to pass through.
Another response to arthritis in the lower back is that ligaments around the joints increase in size. This also lessens space for the nerves. Once the space has become small enough to irritate spinal nerves, painful symptoms result.
Back pain. People with spinal stenosis may or may not have back pain, depending on the degree of arthritis that has developed. Spinal nerves relay sensation in specific parts of your body. Pressure on the nerves can cause pain in the areas that the nerves supply. Pain in the buttocks that radiates down the leg — called sciatica — is caused by this pressure.
Printed with permission from Griffen LY (ed): Essentials of Musculoskeletal Care, Edition 3. Rosemont, IL American Academy of Orthopaedic Surgeons, 2005. p. 770.
Burning pain in buttocks or legs (sciatica). Pressure on spinal nerves can result in pain in the areas that the nerves supply. The pain may be described as an ache or a burning feeling. It typically starts in the area of the buttocks and radiates down the leg. The pain down the leg is often called "sciatica." As it progresses, it can result in pain in the foot.
Numbness or tingling in buttocks or legs. As pressure on the nerve increases, numbness and tingling often accompany the burning pain. Although not all patients will have both burning pain and numbness and tingling.
Weakness in the legs or "foot drop." Once the pressure reaches a critical level, weakness can occur in one or both legs. Some patients will have a foot-drop, or the feeling that their foot slaps on the ground while walking.
Less pain with leaning forward or sitting. Studies of the lumbar spine show that leaning forward can actually increase the space available for the nerves. Many patients may note relief when leaning forward and especially with sitting. Pain is usually made worse by standing up straight and walking. Some patients note that they can ride a stationary bike or walk leaning on a shopping cart. Walking more than 1 or 2 blocks, however, may bring on severe sciatica or weakness.
Source from AAOS, Viewmedica, WebMD