Identification of True Knee Flexion Axis Despite Marker Misplacement Using Principal Component Analysis

Gait analysis is useful for revealing pathologic tibial rotation in children with cerebral palsy (CP), thus guiding interventions of de-rotational osteotomy [1]. Surface marker misplacement may cause an inaccurate definition of the knee flexion axis, which generates downstream artifacts such as cross talk between knee rotation angles and internal rotation errors, misleading these patients’ assessments and surgical interventions [2,3]. Therefore, the purpose of this study was to develop and evaluate a novel method for defining the true knee flexion axis from existing marker trajectories during gait. We hypothesized that the devised method would accurately quantify the offset in the flexion axis due to a systematically misplaced marker and correct the downstream crosstalk and rotation errors of the knee joint angles associated with the marker misplacement.