Inter-examiner and inter-day reliability of dynamic tibiofemoral movements measurement using motion capture during walking and jumping tasks

BACKGROUND: The anterior cruciate ligament (ACL) primarily restricts dynamic anterior tibia translation (ATTd) and internal tibia rotation (ITRd). Measuring these movements dynamically is essential for evaluating injury risk factors and their potential consequences. This study aimed to assess the inter-examiner and inter-day reliability of measuring ATTd and ITRd during walking and jumping tasks using optoelectronic motion capture. METHODS: Nineteen healthy participants performed walking, side hop, single-leg hop for distance, and triple hop for distance. To assess inter-examiner reliability, tasks were repeated on the same day: once after the first examiner placed markers and once after the second examiner. To assess inter-day reliability, tasks were repeated on a second day. Pointwise intraclass correlation coefficient (ICC) and standard error of measurement (SEM) values were assessed across the stance phase of walking and the jump-landing phases. RESULTS: For walking, ICC values over the stance phase indicated good-to-excellent reliability for ATTd and ITRd (ICC = 0.66-0.82), with SEM values below 3.2 mm and 2.8° (≤19 % of range of motion). For all jumping tasks, ICC values over the entire landing indicated excellent reliability for ATTd and ITRd (ICC = 0.75-0.86), with higher inter-examiner compared with inter-day reliability. The phase around peak ground reaction force demonstrated superior reliability compared with the entire landing, with SEM values below 2.6 mm and 2.2° (≤17 % of range of motion, except for ATTd during the side hop). CONCLUSION: Results suggest adequate reliability of ATTd and ITRd for research assessing ACL injury risk factors and outcomes of various surgical and rehabilitation methods following ACL injury.