A common cause of low back and leg pain is lumbar 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 nerve roots is equally common in men and women.
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.
Arthritis is the most common cause of spinal stenosis. Arthritis refers to 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.
When we are young, disks have a high water content (left). As disks age and dry out, they may lose height or collapse (right). This puts pressure on the facet joints and may result in arthritis.
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 facet 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.
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.