Spondylolysis
Spondylolisthesis is a condition in which one of the bones of the spine (vertebrae) slips out of place onto the vertebra below it. If it slips too much, the bone might press on a nerve, causing pain. Usually, the bones of the lower back are affected.

The word spondylolisthesis comes from the Greek words spondylos, which means "spine" or "vertebra," and listhesis, which means "to slip or slide."

What are the types of spondylolisthesis?
There are different types of spondylolisthesis. The more common types include.

Congenital spondylolisthesis: Congenital means "present at birth." Congenital spondylolisthesis is the result of abnormal bone formation. In this case, the abnormal arrangement of the vertebrae puts them at greater risk for slipping.

Isthmic spondylolisthesis: This type occurs as the result of spondylolysis, a condition that leads to small stress fractures (breaks) in the vertebrae. In some cases, the fractures weaken the bone so much that it slips out of place.

Degenerative spondylolisthesis: This is the most common form of the disorder. With aging, the discs - the cushions between the vertebral bones - lose water, becoming less spongy and less able to resist movement by the vertebrae.