Abstract
PURPOSE: To systematically assess published classification systems for knee ligament injuries and to propose a comprehensive, multiplanar, sequential knee ligament classification system that improves upon those in the published literature. METHODS: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. PubMed, Embase, and Cochrane were searched from inception to January 2025 for studies reporting knee classification systems. Inclusion criteria consisted of studies reporting knee classification systems and English language. Exclusion criteria consisted of classifications only describing specific type of knee injuries (e.g., only anterior cruciate ligament injuries). The characteristics of each classification system were recorded and analyzed descriptively. A classification system was proposed that addresses the weaknesses of the existing systems. RESULTS: A total of 6 classification systems were identified in 8 studies in the literature and were published between 1975 and 2009. Existing classification systems were strong in correlating type of injuries with rotatory ligamentous laxity and physical examination findings but were lacking assessment of knee position during injury, discussion of sequence of injuries, involvement of bone marrow edema (except one study), and lack of correlation with knee dislocations. No clinical validation was performed. A knee classification system was created that included sequence of injuries, correlation with knee dislocation and injury mechanism, and bone marrow edema. CONCLUSIONS: Knee injury classification systems lack comprehensive consideration of injury mechanism, sequence of injury, bone marrow edema, meniscus and chondral damage, involved ligaments, rotatory instability, and correlation with knee dislocation. The sequence of injury to these structures could be relevant to understanding injury mechanism and treatment, but requires validation. LEVEL OF EVIDENCE: Level V, systematic review of level IV-V studies.