Spinal stenosis is the narrowing of spaces in the spine (backbone) which causes pressure on the spinal cord and nerves. About 75% of cases of spinal stenosis occur in the low back (lumbar spine). In most cases, the narrowing of the spine associated with stenosis compresses the nerve root, which can cause pain along the back of the leg. This narrowing happens as a result of the degeneration of both the facet joints and the intervertebral discs. In this condition, bone spurs (also called osteophytes) grow into the spinal canal.