Retrolisthesis is a medical term used to describe a condition in which one vertebra in the spine slips backward in relation to the vertebra below it. This is the opposite of anterolisthesis, where the vertebra slips forward. Both retrolisthesis and anterolisthesis are types of spondylolisthesis, which refers to any forward or backward vertebral displacement.
Retrolisthesis can occur in any region of the spine but is most commonly found in the cervical (neck) and lumbar (lower back) regions. It may result from various factors, including degenerative changes, traumatic injuries, congenital abnormalities, or excessive strain on the spine.
Although the picture above represents anterolisthesis, a similar grading is used for retrolisthesis. The vertebral slip is backwards in retrolisthesis.