Despite reported success with TKA surgery, it is unclear based on current tools and clinical monitoring postoperatively, if function at the knee joint-level is being optimized, specifically on a person-specific level. Or where along the functional spectrum of knee OA do individuals in terms of their biomechanics reside post-TKA. The drive to understand the variability in individual response at the knee joint-level is paramount to increasing success with TKA, and for developing objective assessment and evaluation tools for clinic, research, and industry.

The purpose of this study was to comprehensively capture the variability of improvement in knee joint-level biomechanics during walking gait of participants immediately before to one year after TKA, measured objectively using 3D gait analysis. This included examining how the pre-TKA status of knee joint-level biomechanics influences the amount of improvement after TKA, and investigating on an individual level whether joint-level biomechanics, both pre- and post-TKA, are more similar in level of function to healthy controls or those with moderate knee OA. Through calculating the change in biomechanics from pre-to post-TKA for a comprehensive list of biomechanical variables, significant and negative associations were shown between pre-TKA values and the change in values pre-to post-TKA. This suggests that pre-TKA functional status influences functional improvement, with lower function pre-TKA being associated with larger improvements post-TKA. Through investigating the number of individuals with biomechanics within asymptomatic and moderate OA ranges, it was shown both univariately and when multiple biomechanical variables were combined using a multivariate distance approach, that the majority of individuals post-TKA reach levels of knee joint function most similar to those with moderate levels of OA.

This study also examined the hierarchy of knee joint-level biomechanics in TKA to best summarize the functional variables that are most targeted by current standard of care TKA, and those that remain deficient post-TKA. Three discriminant models, with a stepwise procedure for variable selection, were developed using an optimal set of biomechanics to separate knee joint-level function during walking gait of individuals preand post-TKA, and from healthy controls. It was shown that current TKA management predominately alters variables of the frontal plane, resulting in relatively large deficits in sagittal plane knee joint function between TKA recipients and healthy controls. The discriminant models allowed for the development of a single functional score, able to quantify the functional gap in knee joint level biomechanics throughout triage with TKA.

The results of this study provide a comprehensive look at the variability in knee joint level improvement with TKA on a person-specific level and contribute to a framework for optimizing outcome from TKA based on objective person-specific data.