Spondylolisthesis is caused when one of the vertebrae in the spine begins to slide forward or backward over the bone below. Though it typically occurs in the lower spine, it may also be seen across the spine’s entirety. In some patients, the condition may also cause the spinal cord or nerve roots to be squeezed. Should this happen, a patient may experience symptoms such as leg numbness or weakness or back pain. The origin of spondylolisthesis may be congenital, degenerative, or traumatic in its origin. Its symptoms may also include pain, stiffness, and muscle spasms.