Spinal stenosis causes a constriction of the space for nerves in the spine.
In the back of the lumbar spine, each vertebra has an opening that contains a bundle of nerves.
On each side, a nerve root branches off and exits the spine through a space in the back of the vertebra called the foramen.
Normally, there is plenty of room for the nerves in the spinal canal and for the nerve roots exiting the spine.
With lumbar spinal stenosis, degenerative changes, such as bone spurs, can constrict the space for the nerves in the spinal canal.
Bone spurs and other problems can also affect the foramen, constricting the space for a nerve root as it exits the spine.
Symptoms of lumbar spinal stenosis may include pain and/or weakness or numbness that radiate from the lower back into the leg.