Background Stiff landings with less knee flexion and high vertical ground reaction force have shown to be associated with increased risk of ACL injuries (Leppänen et al. 2016). The association between other sagittal plane measures and the risk of ACL injuries is less studied in prospective study designs.

Objective To investigate the relationship between selected sagittal plane hip, knee, and ankle biomechanics and the risk of ACL injuries in young female team sport players.

Design Prospective cohort study.

Setting Female youth team sports.

Participants A total of 171 female basketball and floorball players (aged 12–21) participated in a VDJ test using 3D motion analysis. All new ACL injuries, as well as match and training exposure, were recorded for 1 to 3 years.

Assessment of Risk Factors The following biomechanical variables were analysed: 1) peak knee extension moment, 2) peak hip flexion angle, 3) peak hip extension moment, and 4) peak ankle dorsiflexion angle. Cox regression models were used to calculate hazard ratios (HRs, adjusted for 10 unit change) and 95% confidence intervals (CIs).

Main Outcome Measurements Non-contact ACL injuries.

Results Subjects suffered a total of 15 ACL injuries during the follow-up (0.2 injuries per 1 000 player hours). Of the investigated variables, landing with decreased hip flexion was significantly associated with increased risk of ACL injury (HR 0.60; 95% CI 0.37 to 0.97, P=0.038). Peak knee extension moment (HR 1.13; 95% CI 0.79 to 1.62, P=0.490), peak hip extension moment (HR 0.88; 95% CI 0.77 to 1.01, P=0.065), and peak ankle dorsiflexion angle (HR 0.70; 95% CI 0.33 to 1.51, P=0.360) were not significantly associated with ACL injuries.

Conclusions Landing with less hip flexion may increase the risk of ACL injury in young female team sport players. More studies with large study populations are needed to confirm these findings.