Claims-based data describe a bimodal age distribution of hamstring injuries in the United States, but the underlying mechanisms remain unclear. We queried the National Electronic Injury Surveillance System for upper-leg strain or sprain injuries from 2015 to 2024; cases containing hamstring-specific narrative terminology were classified through hierarchical review of product codes and narrative text. Among 1,651 hamstring-specific cases (71,285 estimated nationally; 95% CI, 55,475 to 87,096), sport-related mechanisms accounted for 94.1% of injuries among patients aged 10 to 19 years versus 23.8% among those aged 60 years and older (p < 0.01). After adjustment for sex, adolescents had a sport-related mechanism prevalence ratio of 3.88 relative to older adults (95% CI, 3.02 to 4.98), with a graded gradient across intermediate strata. Sport-related and non-sport injuries differed in mean age, sex distribution, and admission rate, supporting their characterization as distinct injury patterns warranting age-tailored prevention strategies.
Keywords: Hamstring; ageing; athletes; epidemiology; strain.