Normalized gait analysis parameters are closely related to patient-reported outcome measures after total knee arthroplasty

Up till now, only a weak connection could be shown between patient-related outcome measures (PROMs) and measurements obtained by gait analysis (e.g. speed, step length, cadence, ground reaction force, joint moments and ranges of motion) after total knee arthroplasty (TKA). This may result from the methodical problem that regression analyses are performed using data that are not normalized against a healthy population. It does appear reasonable to assume that patients presenting a physiological gait pattern are content with their joint. The more the gait parameters differ from a normal gait pattern the worse the clinical outcome measured by PROMs should be expected to be. In this retrospective study, 40 patients were enrolled who had received a gait analysis after TKA, and whose PROMs had been evaluated. A gender- and age-matched control group was formed out of a group of test persons who had already undergone gait analysis. Gait analysis was undertaken using the motion analysis system 3D Vicon with ten infrared cameras and three strength measuring force plates. The physiological gait analysis parameters were deduced from arithmetic mean values taken from all control patients. The deviances of the operated patients’ gait analysis parameters from the arithmetic mean values were squared. From these values, the Pearson correlation coefficients for different PROMs were then calculated, and regression analyses were performed to elucidate the correlation between the different PROMs and gait parameters. In the regression analysis, the normalized cadence, relative gait speed of the non-operated side, and range of the relative knee moment of the operated side could be identified as factors which influence the Forgotten Joint Score (FJS-12). The explanation model showed an increase of the FJS-12 with minimisation of these normalized values corresponding to an approximation of the gait pattern seen in the healthy control group. The connection was strong, having a correlation coefficient of 0.708. A physiological gait pattern after TKA results in better PROMs, especially the FJS-12, than a non-physiological gait pattern does.