A common cause of low back and leg pain is lumbar spinal stenosis.
As we age, our spines change. These normal wear-and-tear effects of aging can lead to narrowing of the spinal canal. This condition is called spinal stenosis. 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.
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 nerve roots is equally common in men and women.
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.
What is the anatomy of the spine?
Your spine is made up of small bones, called vertebrae, which are stacked on top of one another. Muscles, ligaments, nerves, and intervertebral discs are additional parts of your spine.
What causes spinal stenosis?
Arthritis is the most common cause of spinal stenosis. Arthritis refers to the breakdown of any joint in the body.
In the spine, arthritis can result as the disc breaks down and loses water content. In children and young adults, discs have high water content. As we get older, our discs begin to dry out and weaken. This problem causes settling, or collapse, of the disc spaces and loss of disc space height.
As the spine settles, two things occur. First, weight is transferred to the facet joints. Second, the tunnels that the nerves exit through become smaller.
As the joints experience increased pressure, they also begin to degenerate and develop arthritis, similar to that occurring in 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.
Also, when arthritis develops in the lower back, ligaments around the joints increase in size meaning there is even less space for the nerves. Once the space has become small enough to irritate spinal nerves, this is what causes the pain.
What are symptoms of spinal stenosis?
Back pain. People with spinal stenosis `may or may not have back pain, depending on the degree of arthritis that has developed.
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. 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.