Damage to bones or joints can cause vertebrae to slip forward, distorting the Spinal Cord. This is called Spondylolisthesis. There are two types of this condition – Degenerative and Isthmic. In both cases, the patient may experience pain in the legs and feet from pinched Nerve Roots. With Degenerative Spondylolisthesis, the joints weaken, allowing a vertebra to slip forward. Isthmic Spondylolisthesis occurs when vertebral bones become fractured.