Avulsion of lumbar vertebral rim plate is an uncommon lesion, seen specially in young adults. Its occurrence in pediatric age is very infrequent. As with intervertebral disc herniation in children, an accurate diagnosis may be often delayed due to concerns for neoplasm, infection, and spondylolisthesis. We report a 15-year-old boy with symptoms and myelographic details of disc protrusion. Plain radiographs, computerized tomography of the lumbar spine, and operative findings showed that the cause of root compression was a slipping of the entire disc together with the posterior rim plate at the L4-5 space. Pertinent literature on the subject is briefly reviewed. The proposed mechanism for apophyseal ring fracture is a combination of two factors: congenital insufficiency of the rim plate and injury to the lumbar spine.