Definition: Spondylolysis is a word that is used to describe a condition where there is a defect in a specific region of the spinal column. This region of the spinal column, called the pars interarticularis, connects adjacent vertebrae in the spine.
Spondylolysis can be asymptomatic, or it can be quite painful. When the condition is bilateral (occurs on both sides of the spine) it can cause a condition called spondylolisthesis. In this condition, a vertebral body can "slip" forward over the vertebrae directly below. The reason this occus is that the normal stuctures that connect adjacent vertebrae are missing, and therefore the spinal column become unstable.
