Courses of change in knee adduction moment and lateral thrust differ up to 1year after TKA.

Abstract

In total knee arthroplasty (TKA), dynamic knee loading may loosen the artificial joint and bone or cause polyethylene wear after prolonged use. TKA decreases knee adduction moment at 6months, but this effect is lost by 1year post-operatively. However, lateral thrust after TKA has not been clarified. We hypothesized that like knee adduction moment, lateral thrust would return to baseline levels by 1year post-operatively. Participants were 15 patients who underwent TKA for medial knee OA. Japanese Orthopaedic Association (JOA) score, numeric rating scale, and gait analysis (measurement of peak knee adduction moment, knee varus angle at peak knee adduction moment, lateral thrust, and gait speed) were performed preoperatively (baseline) and 3weeks, 3 and 6months, and 1year post-operatively. JOA score improved from 55±9.8 to 78±12.1 at 1year post-operatively, and pain decreased significantly from baseline at each follow-up (p<0.001). Significant increases in gait speed were observed at 6months and 1year (p<0.001). Peak knee adduction moment during stance phase was significantly lower at 3weeks, 3months, and 6months compared to baseline (p<0.05), but no significant changes were seen at 1year. Knee varus at peak knee adduction moment did not differ significantly between any measurement points, while lateral thrust was decreased at 6months and 1year compared to baseline (p<0.05). Temporal courses of changes up to 1year after TKA differed between knee adduction moment and lateral thrust, so our hypothesis was rejected. IV.