Spondylolisthesis is a slipping of vertebra that occurs, in most cases, at the base of the spine, due to a defect or fracture of one or both wing-shaped parts of a vertebra. This defect, called spondylolysis, can result in vertebrae slipping backward, forward or over a bone below.

Spondylolisthesis is commonly caused by stress on the bones in the lower back resulting in a fracture or multiple micro-fractures. Degeneration from aging or overuse, tumors or other trauma may also cause spondylolisthesis. In some cases, spondylolisthesis is congenital (present at birth).

Pain usually spreads across the lower back and may feel like a muscle strain.

Spondylolisthesis can cause spasms that stiffen the back and tighten the hamstring muscles, resulting in changes to posture and gait. If the slippage is significant, it may begin to compress the nerves and narrow the spinal canal.

Pain may also be felt in the buttocks or radiating down the legs (due to pressure on nerve roots).