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Chapter 482pass frequency convolution filter of 10 Hz with no lag. Software was used to fill any gaps in the data when there was a temporary (maximum gap of ten frames) absence of marker identification. When a trial contained gaps exceeding 2.5ms, smoothing of the data could not be performed, and was therefore rejected. In order to quantify tibial rotation and anterior tibial translation, two coordinate systems were reconstructed in the tested knee using the customized MATLAB script based of the method of Boeth et al.6 The parent system was reconstructed in the femoral segment and the child system in the tibial segment. The motion of each coordinate system was consistent with the movement of the respective segment. ATT was quantified in millimeters using the relative movement of the center of rotation of the tibial coordinate system to the center of rotation of the femoral coordinate system in the local tibial coordinate system. rTR was quantified by the angle between the two axes of rotation, as described by Keizer and Otten.22Only the data of the reconstructed knee was used in the analysis.Patient reported outcome measuresTo assess self-reported knee function and psychological readiness, the International Knee Documentation Committee (IKDC) questionnaire and the Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) scale were used. Both are validated patient reported outcome measures for ACLinjured and reconstructed population. The validated Dutch translations were used.18,20,42 The IKDC is one of the most used PROMs for ACL-injured population.17,21 It is designed to measure function, symptoms, and sports activity. A higher score indicates a higher level of knee function and less knee symptoms.17 The ACL-RSI measures psychological readiness to return to sport after ACL-reconstruction.47 It is designed to measure emotions, confidence, and risk appraisal.31,47 A higher score indicates greater psychological readiness for return to sport.31Statistical analysisThe statistical analysis was performed using SPSS (v27; IBM Corp, Armonk, NY, USA). The correlation between the objective lower limb measures (rTR, ATT) and self-reported measures (IKDC, ACL-RSI) was examined by calculating Pearson’s correlation coefficients. These coefficients Mark Zee.indd 82 03-01-2024 08:56