Comprehensive Arthroscopic Characterization of Discoid Meniscus Tears and Instability Using the PRiSM Discoid Meniscus Classification

The discoid meniscus is a congenital abnormality, with the vast majority occurring in the lateral meniscus. More commonly seen in pediatric populations, patients present with acute or chronic knee symptoms such as joint line pain, audible or palpable mechanical symptoms, and the inability to achieve terminal extension. The classic discoid classification system by Watanabe excludes anterior and horizontal instability and tearing that commonly occur with this pathology. A comprehensive classification, the Pediatric Research in Sports Medicine (PRiSM) Discoid Meniscus Classification, was developed to include these characteristics. To complement this classification system, we describe a complete arthroscopic examination of the discoid meniscus, assessing meniscal width, height, instability, and tearing. For thorough anterior assessment, the importance of medial portal viewing with lateral portal probing is highlighted. Assessment of the meniscus for tearing and instability should be performed before and after saucerization. Consistent use of a comprehensive classification system and a diagnostic arthroscopic exam will improve the understanding, treatment, and quality of research in the discoid meniscus.