Spondylolisthesis is the condition in which one vertebral body is slipped forward over another. Spondylolisthesis is most likely caused by an underlying condition of spondylolysis. There are different types of spondylolisthesis, including degenerative, isthmic, dysplastic, traumatic, and pathologic. Isthmic spondylolisthesis is the most common cause of back pain in adolescents and the typical symptom is back and/or leg pain that limits a patient's activity level. Patients with spondylolisthesis are often advised not to participate in rigorous activity such as sports in order to avoid neurological damage or paralysis, but cases are rare and for the most part, it is not a dangerous condition. Most adolescents with spondylolisthesis do not actually experience any symptoms or pain.