Background Turner’s syndrome, discoid meniscus, and Blount’s disease have all been studied in isolation, but, to the best of our knowledge, there have been no studies reporting a patient with all three. Thus, the first case of Turner’s syndrome with discoid meniscus and Blount’s disease is presented. Case presentation A 5-year-old Japanese girl with a history of Turner’s syndrome and Blount’s disease complained of pain in her left knee. Magnetic resonance imaging showed a discoid lateral meniscus tear, and arthroscopic partial meniscectomy was performed, providing a good outcome. Conclusions In this report, some possible explanations regarding the concomitant presence of these three diseases are discussed. A possible explanation in this case is that the patient with Turner’s syndrome had a discoid lateral meniscus that might have been induced by some genetic factors associated with Turner’s syndrome, and then the discoid lateral meniscus might have been the mechanical stress that caused Blount’s disease.