Does Total Knee Arthroplasty Reproduce Natural Knee Mechanics

Abstract

As the number of total knee arthroplasty (TKA) procedures increases annually, the patient demographic is shifting to include younger patients with higher expectations for post-operative function. The aim of this study was to compare movement patterns during activities of daily living among TKA patients and a healthy, age-matched group using 3D motion analysis. Specifically, this analysis looked at walking on level and inclined surfaces, as well as sitting up and down from a chair. It was predicted that (1) TKA patients would exhibit reduced knee extension moments at the operated limb and increased adduction moments at the contralateral limb during gait, (2) walking downhill would result in greater differences between TKA and control groups, compared to level walking, and (3) TKA participants would have greater flexion angles, moments and power values at the hip, compared to controls, during the sit-stand tasks. Seventeen participants (age=62±6 years, BMI=30±3 kg/m2, time after surgery=11±5 months) were recruited from the Ottawa Hospital, having undergone unilateral TKA by the same surgeon. An age-matched control group was composed of 17 individuals (age=63±8 years, BMI=27±4 kg/m2) who were recruited from the local community. Three dimensional (3D) biomechanical assessment was conducted with all participants performing five trials of walking on level and inclined surfaces, stair ascent and descent as well as sit-stand tasks. Results from this study were focused on gait and sit-stand transitions, showing that TKA participants exhibited altered gait patterns on both walking surfaces, with significantly smaller knee flexion angles and moments, as well as reduced peak power at the knee. The TKA group also experienced reduced knee extension moments; however, this was only significant for downhill walking. Consistent with our hypothesis, downhill walking resulted in greater discrepancies between the groups compared to level walking. Contrary to our third hypothesis, TKA participants exhibited significantly smaller peak hip flexion angles and moments during the sit-stand task, along with reduced hip abduction angles and knee abduction moments. The reduced knee flexion kinematics and kinetics observed during gait tasks, combined with the differences in frontal plane mechanics observed during the sit-stand task suggest that altered loading patterns persist six to twelve months after surgery. This may be a result of continued pre-operative movement patterns as well as the surgery itself, and should be kept in mind when developing rehabilitation programs for this patient population.