Even though it is a big word,  the meaning of spondylolisthesis is simple – slipped vertebrae. It occurs when a vertebra slips forward and is over the vertebra beneath it. This happens most commonly in the lower back where the spine carries more weight and  pressure. While some types of pain are the result of acute injuries and heal quickly, others can, if left untreated, lead to severe lower back pain. If you are suffering from consistent back pain, it is important to get a diagnosis so you can begin treatment.