Redefining Injury Severity in Youth Sports: Functional Inability to Walk as a Primary Severity Phenotype (n = 4,829)

Abstract Objectives Determinants of functional injury severity in young athletes remain incompletely understood. Conventional assumptions emphasize contact sport participation and skeletal immaturity as major drivers of severe injury; however, severity definitions based on surgery or time loss are strongly influenced by health-care systems and competition contexts. We investigated factors associated with early functional severity after lower-extremity sports injury using a large clinical cohort. Methods This cross-sectional observational study analyzed 4,829 lower-extremity sports injury cases in athletes aged ≤22 years who presented to a specialized sports injury clinic between January 2017 and November 2025. Severe injury was defined as inability to walk independently at the initial visit. Multivariable logistic regression analysis was performed to evaluate associations between severe injury and age, sex, sport type, injury mechanism, injury location, and physeal status. Results Severe injury was most strongly associated with acute injury compared with overuse injury (odds ratio [OR], 31.1; 95% confidence interval [CI], 17.7–54.6; p