Methods / Statistics

Document Type



Inter-limb differences in frontal plane knee loading have been observed during change of direction tasks following anterior cruciate ligament reconstruction. Objective assessment of these differences may be a useful means of monitoring rehabilitation, but their robustness to methodological sources of error such as marker placement must be established prior to any clinical implementation. The aim of this investigation was to determine the effect of random marker placement error on the interpretation of inter-limb differences in frontal plane knee loading during a change of direction task. Participants completed three trials of a 90° change of direction task on both limbs. Simulated displacements were applied to the lateral thigh, femoral epicondyle and tibia markers. Inter-limb differences in peak knee abduction moment were calculated in each condition. A 95% confidence interval of ± 0.52 Nm/kg was identified for inter-limb differences in knee abduction moment. Marker placement variability thus limits the ability to identify smaller changes in inter-limb differences over repeated tests.