Exemplar PC reconstruction using the first three principal components (PCs) of the knee flexion waveforms during the gait cycle.

The mean and ±1 STD waveforms of 30 non-pathological (NP) and 30 osteoarthritic (OA) subjects are plotted for individual reconstructions of the first three principal components (PC1-3). The exemplar waveforms and intended to demonstrate how different PCs represent different modes of variation across the waveforms. For example, PC1 reconstructs variation in magnitude of knee flexion during stance phase which isn’t discriminatory of OA gait. The reconstruction using PC2 highlights that this component represents changes in range of motion throughout the stance phase of gait, which is related to a reduced and delayed peak knee flexion during swing phase. The third PC reconstructs only 13% of variance of all the waveforms–primarily representing differences during terminal swing phase of gait.