The adolescent athletes are at greater risk of low back pain and structural spine injuries. Spondylolysis is responsible for the majority of back pain cases in young athletes, rarely occurring in adults. We report a case of a 13-year-old judo female athlete, who came to our service with 5 months of progressive low back pain during training which was initially attributed to mechanical causes, without any further investigation by imaging methods. At admission, the patient had lumbar deformity, antalgic posture and bilaterally positive unipodalic lumbar hyperextension maneuver. After a research which showed spondyloptosis, the patient underwent surgery. In this article, we discuss, based on this case report, the diagnostic approach to low back pain in young athletes, since the complaint of chronic back pain can be a marker of a structural lesion that may be permanent and bring irreversible functional loss.