Spondylolisthesis refers to a slipped vertebra, i.e. a displacement of the upper vertebra with respect to the lower one. This can occur degeneratively due to joint wear or due to a disruption of the vertebral arch, which is usually a consequence of an unnoticed and unhealed fracture. A slipped vertebra often becomes symptomatic through an instability-related pain on exertion (getting up from a chair is only possible with the help of the arms). However, it is not uncommon for the vertebral displacement to lead to secondary spinal canal stenosis, which then becomes noticeable as pain extending into the legs.

X-ray image of a slipped vertebra in the lower lumbar spine before and after surgery