Predictors of multidimensional functional outcomes after total knee arthroplasty.

Multiple assessments are used clinically after total knee arthroplasty (TKA) including self-report, performance tasks, and physical activity levels. It is unclear if these different functional assessments are interchangeable or if they measure different constructs. The objective of this study was to characterize different functional measures before and after TKA. We characterized function before and after TKA using perceived function (KOOS ADL), physical performance (gait speed), and daily activity (steps/day via accelerometry); compared function in people undergoing TKA to age-matched healthy controls; and examined characteristics of those undergoing TKA for potential predictors of postoperative function. Prior to TKA, all three functional assessments were significantly lower for participants than those of healthy controls and each measure remained lower for participants than for controls postoperatively. All three functional assessments developed differently over time postoperatively. Each functional outcome had a unique set of predictors. Perceived function was predicted primarily by anxiety and depression, physical performance was most strongly predicted by age, and daily activity was chiefly predicted by BMI. Pressure pain threshold was a common predictor across all models. Functional limitations exist preoperatively and persist postoperatively across different measures in people undergoing TKA when compared to those measures in healthy controls. Functional outcomes after TKA are different depending on the functional measure utilized, implying that different constructs underlie each measure. Multiple functional measures should be assessed to provide a more comprehensive assessment of function after TKA. Further work should assess the impact of interventions designed to treat modifiable predictors of postoperative TKA function. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2790-2798, 2017.