Koga et al.55 analyzed movement characteristics of 10 ACL injury cases in female team handball and basketball using the model-based manual image-matching technique. They estimated that injuries occurred about 40 ms after initial foot contact with the ground. Knee flexion and knee valgus increased during the first 40 ms after the initial foot contact with the ground, and that the knee was externally rotated at initial foot contact with find more the ground, and internally rotated during the first 40 ms after the initial foot contact. The investigators concluded that the valgus motion coupled with internal tibial rotation

under low knee flexion appeared to be important risk factors for ACL injury.55 However the measurement errors of the model-based manual image-matching technique were up to 11° in knee flexion angle, 13° in knee internal/external rotation angle, and

5° in knee varus/valgus angle.54 These significant measurement errors AZD6738 solubility dmso minimized the validity of this study. Another method to identify risk factors for ACL injury is to determine associations of injury risk factors with pre-injury movement characteristics through prospective cohort studies. In a prospective cohort study,56 205 adolescent soccer, basketball, and volleyball players were screened for lower extremity biomechanics in a drop landing task, and subsequently followed for 13 months. Nine ACL injuries (seven in soccer and two in basketball) occurred. Compared already to the non-injured players, the injured-players had increased knee abduction angles at initial contact, maximum knee abduction angles, maximum external knee abduction moments, peak vertical ground reaction

forces, maximum external hip flexion moments, and side-to-side knee abduction moment differences during landing, and decreased maximum knee flexion angles and stance time. Statistical analysis demonstrated that the knee abduction moment was the most sensitive factor to predict ACL injury with 75% specificity and 78% sensitivity. This was the first prospective cohort study in an attempt to screen jump-landing mechanics to identify biomechanical risk factors for ACL injury. However a small number of injuries, the late occurrence of the maximum knee valgus moment during the stance phase, a lack of horizontal deceleration in the testing task, and a lack of consideration of ACL loading mechanisms were identified as limitations of this study.23 Also a lack of cause-and-effect relationship between identified risk factors and the injury risk is another significant limitation of this type of prospective cohort study. Another study to prospectively identify risk factors for ACL injury was performed at three US military academies for 5 years.57 A total of 6124 cadets were screened for lower extremity biomechanics in a simulated stop-jump task. Ninety-eight cadets had ACL injuries after the screening.