Lumbar refers to the low back area. The last five vertebral bones in the spinal column make up the lumbar spine. The canal is a round, open space that allows the spinal cord to go from the brain down to the start of the lumbar spine. Stenosis refers to a narrowing of that canal.
Stenosis often occurs with the degenerative aging process. The bones start to collapse. The discs in between the vertebrae thin out and may even fuse to the bone. Ligaments along the back of the vertebrae to support the spine become thickened. All of these changes cause narrowing or stenosis of the spinal canal. Bone spurs around the joints are another change that can cause lumbar stenosis.
The pain and weakness come from pressure on the spinal nerves as they exit the spinal canal. Sometimes exercise helps and people try that first. Anti-inflammatories are frequently used with success in about 50 percent of the cases. Surgery to decompress or take pressure off the spinal nerves may be advised.