Boys demonstrate greater knee frontal moments than girls during the impact phase of cutting maneuvers, despite age-related increases in girls

PURPOSE: Anterior cruciate ligament (ACL) injury rate is low among children, but increases during adolescence, especially in girls. Increases in the knee valgus moment within 70 ms of contact with the ground (KFM(0-70)) may explain the sex-specific increase in the risk of ACL injury. The purpose of the study was to investigate sex-dependent changes in the KFM(0-70) from pre-adolescence to adolescence during a cutting maneuver (CM). METHODS: Kinematic and kinetic data during the CM task, performed before and after physical exertion, were recorded using a motion capture system and a force plate. A total of 293 team handball and soccer players, aged 9–12 years, were recruited. A number of those who continued sports participation (n = 103) returned five years later to repeat the test procedure. Three mixed-model analysis of variance (ANOVA) for repeated measures tests were used to determine the effects of sex and age period on the KFM(0-70) (1: with no adjustment, 2: adjusted for repeated measurements, and 3: additionally adjusted with hip and knee joint frontal plane kinematics). RESULTS: Boys had significantly higher KFM(0-70) than girls at both age periods (p < 0.01 for all models). Girls, not boys, demonstrated significantly increased KFM(0-70) from pre-adolescence to adolescence. Importantly, this was fully explained by kinematic variables. CONCLUSION: Although the marked increase in KFM(0-70) seen in girls may play a role in their risk of ACL rupture, the higher values demonstrated by boys during CM reflect the complexity of multifactorial biomechanical risk factor analysis. The role of kinematics in mediating the KFM(0-70) provides means for modification of this risk factor, but as boys had higher joint moments, continued investigation into sex-dependent biomechanical risk factors is warranted. LEVEL OF EVIDENCE: II. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00167-023-07340-z.