Lumbar stenosis is a condition in which the spinal canal (where spinal nerves pass) is narrowed and causes symptoms by compression of the spinal nerves. It can be subdivided into congenital stenosis and acquired stenosis.
Congenital stenosis simply means that a person is born with a narrowed spinal canal. This can occur with particular diseases; however, it can also occur in the general population (who do not have any particular disease conditions). Most people remain asymptomatic until a minor degenerative process causes further narrowing of the spinal canal.
Acquired stenosis occurs due to degenerative changes. With degeneration of the disc, the height of the disc decreases while the width of the disc increases, accompanied by protrusion of the disc and bone spur formation at the edge of the vertebrae. The facet joints, which are the two sliding articular joints at the posterior portion of the spinal motion unit, develop arthritic changes that consist of bone spur formation and overgrowth of the joint capsule. Narrowing of the spinal canal (lumbar stenosis) occurs with the combination of changes in the disc and facet joints.