ACL INJURY-RELATED KINEMATIC ASSESSMENT: A PRELIMINARY STUDY TO COMPARE MARKER-BASED, WEARABLE, AND MARKERLESS SYSTEMS

Anterior cruciate ligament (ACL) injuries often occur in non-contact situations, highlighting the need for effective risk assessment tools. This study compared kinematic outcomes of IMUs (Xsens), markerless (OpenCap) and an optoelectronic system (OMS) – considered the gold standard - in drop jumps with change of direction. Knee and hip sagittal and frontal plane kinematics were recorded concurrently with all three systems in a total of 260 trials. Xsens showed high validity for knee flexion (R2=0.81, RMSE<5°) but lower accuracy in the frontal plane, especially in knee abduction (R2=0.00), limiting its use in ACL injury prevention research. OpenCap had weaker agreement with OMS (i.e., for knee flexion R2=0.76, RMSE=7.6°) and more technical issues. Although both Xsens and OpenCap are useful tools for on-field assessments, overcoming the limitations of the in-lab assessment, their suitability for precise injury screening settings requires further investigation.