Biomechanical Risk Factors for Anterior Cruciate Ligament Injury in a Young Female Basketball Player: A pilot Study

ObjectivesThis study was aimed to reveal the differences in knee valgus angle at landing as a static indicator and wobbling movement of the knee during landing as a dynamic indicator between ACL injury and uninjured athletes. MethodsThis study was case-control study. There were 6 female basketball players with ACL injuries and 38 female basketball players without them, whose knee kinematics were measured using 2-dimensional video cameras during single-leg jump landings. The task was performed from 30cm-box. Knee kinematics and wobbling of the knee which was calculated by relative frontal motion to the flexion movement were compared between knees with ACL-injured and uninjured. ResultsSix athletes who had confirmed ACL injuries, did not demonstrate significantly different knee valgus angle at initial contact and maximum knee flexion during landing, compared to 38 uninjured athletes. The knee valgus angles at initial contact for injured and uninjured athletes were 12.3{degrees} and 14.8{degrees} (p = 0.15), respectively. Five of six anterior cruciate ligament injured knees presented knee wobbling during landing. Relative frontal motion at 18{degrees} knee flexion was significantly greater in athletes with ACL-injured (p = 0.02). Conclusions84% of ACL injury presented with the knee wobbling and the frontal knee motion was greater with low knee flexion during knee wobbling, while the knee valgus angle was not significantly different. This study suggests that knee wobbling may be a biomechanical and dynamic risk factor for ACL injury in female basketball players. Summary BoxWhat is already known on this topic - summarise the state of scientific knowledge on this subject before you did your study and why this study needed to be done Biomechanical risk factor for ACL injury was revealed as dynamic knee valgus and low knee flexion which increases ACL strain. However, previous study focused only static index which are knee angle at initial contact or maximum. This study aimed to establish new dynamic index for screening of ACL injury. What this study adds - summarise what we now know as a result of this study that we did not know before Although a previous study identified knee valgus angle and knee valgus moment as predictors of ACL injury, many athletes who demonstrates knee valgus motion does not suffer ACL injury. Cadaveric studies show that ACL strain did not increase when knee valgus occurred with slowed knee flexion movement. We identified an abnormal knee movement involving the dynamic knee valgus with low knee flexion, which we call "knee wobbling." How this study might affect research, practice or policy - summarise the implications of this study ACL injury has been difficult to predict; however, we found that knee wobbling, which is new parameter of abnormal knee movement, including rapid knee valgus/varus, is a potential predictor of ACL injury.