Prevalence of Discoid Meniscus during Arthroscopy for Isolated Lateral Meniscal Pathology in the Pediatric Population

Background: Meniscus tears in the young patient are becoming more prevalent. Knowledge of presenting characteristics and morphology can affect treatment decisions. The purpose of this study was to review and evaluate all the isolated lateral meniscus pathology that required arthroscopic treatment in a pediatric sports medicine practice and compare presenting characteristics between those with a discoid meniscus and those with normal meniscal morphology. Methods: We performed a retrospective review of all isolated lateral meniscus arthroscopic procedures from 2003 to 2012 in a high-volume pediatric sports practice. Presentation, radiographs, and intraoperative findings were reviewed. The prevalence and clinical findings of a discoid meniscus in this population and among all age groups were compared with those with a meniscus tear occurring in a normal meniscus. Results: Two hundred and sixty-one arthroscopies were performed for symptomatic isolated lateral menisci pathology. Of these, 75% were discoid in nature; the remainder was tears occurring in normal menisci. Ninety-six of 99 patients (97%) with lateral meniscus pathology under the age of 13 had a discoid meniscus and 66% presented with no injury. There was a transition within the population at 14 years of age, with a rise in the incidence of normal meniscal body tears. Even after this transition point, meniscal pathology incidence remained notable; 59% of isolated lateral meniscus pathology in patients between the ages of 14 and 16 years old were a discoid meniscus. Magnetic resonance imaging criteria for discoid meniscus (3 consecutive sagittal cuts or coronal mid-compartment measure) were unreliable after the age of 13 years old. The ratio of complete to incomplete discoids in all age groups was 4 to 3. Conclusions: In conclusion, discoid menisci have a high prevalence in isolated lateral meniscus pathology requiring knee arthroscopy. Clinical presentation, imaging, characteristics, and treatment may be different among different age groups. In the adolescent age group (14 to 16 y old), the presentation of a discoid meniscus may not be different from a meniscus tear with normal morphology. Level of Evidence: Level III - diagnostic.