Degenerative spondylolysthesis is a common condition that affects many individuals over the age of 40. It occurs when the disc and facets wear out and the vertebra above slips forward on the one below. The symptoms can be a sensation of instability (certain motions such as bending or lifting yield a feeling of a give-way in the back or a fear of your back going out) or pelvis and leg pain. The pain in the pelvis, buttocks or sacroiliac joints is typically a feeling of numbness, fatigue, weakness or the legs just giving out with standing or walking. This production–Degenerative Spondylolysthesis Explained Video–describes the anatomy of this disorder, what happens to the spine and how bending forward and standing affect the spinal canal.