The prevalence of spondylolisthesis ranges from 6% to 9% of the population, depending on the etiology studied and screening tools employed.1,2 Spondylolisthesis has not been reported in utero, in non-ambulatory patients, or mammals other than humans, implicating weight bearing forces unique to the upright bipedal spine. Spondylolisthesis and spondylolysis (a defect in the posterior arch without slip or translation) are seen in 4% of children at 6 years of age, 6% at maturity, and as many as 47% of athletes in high-risk sports such as gymnastics.1,2,3 Back pain is the most common complaint, but neurologic involvement may be seen with associated stenosis or progression and deformity. Children diagnosed prior to skeletal maturity or with slips greater than 50% are most likely to progress.4