Abstract
BackgroundThe Six-minute walk (6MW) and Timed-Up-and-Go (TUG) are short walk tests commonly used to evaluate functional recovery after total knee arthroplasty (TKA). However, little is known about walking capacity of TKA recipients over extended periods typical of everyday living and whether these short walk tests actually predict longer, more functional distances. Further, short walk tests only correlate moderately with patient-reported outcomes. The overarching aims of this study were to compare the performance of TKA recipients in an extended walk test to healthy age-matched controls and to determine the utility of this extended walk test as a research tool to evaluate longer term functional mobility in TKA recipients.MethodsThe mobility of 32 TKA recipients one year post-surgery and 43 healthy age-matched controls were assessed using the TUG, 6MW and 30-minute walk (30MW) tests. The latter test was repeated one week later. Self-reported function was measured using the WOMAC Index and a physical activity questionnaire.Results30MW distance was significantly shorter amongst TKA recipients (mean 2108 m [95% CI 1837 to 2381 m]; Controls 3086 m [2981 to 3191 m], P < 0.001). Test-retest repeatability was high (ICC = 0.97, TKA; 0.96, Controls). Amongst TKA recipients, the 30MW distance correlated strongly with the shorter tests (6MW, r = 0.97, P < 0.001; TUG, r = −0.82, P < 0.001). Multiple regression modeling found 6MW distance to be the only significant predictor (P < 0.001) of 30MW distance, explaining 96% of the variability. The TUG test models were moderate predictors of WOMAC function (55%) and physical activity (36%) and were stronger predictors than 6MW and 30 MW tests.ConclusionsThough TKA recipients are able to walk for 30 minutes one year post-surgery, their performance falls significantly short of age-matched norms. The 30MW test is strongly predicted by 6MW test performance, thus providing strong construct validity for the use of the 6MW test in the TKA population. Neither a short nor long walk test is a strong predictor of patient-reported function after TKA.
Highlights
The Six-minute walk (6MW) and Timed-Up-and-Go (TUG) are short walk tests commonly used to evaluate functional recovery after total knee arthroplasty (TKA)
We reasoned that a 30-minute walk (30MW) test was in accordance with patient expectations for functional mobility one year after TKA
Subgroup analysis found that for TKA participants who rested (n= 12), 6MW speed was 0.90 m/s compared to 30MW speed of 0.82 m/s (P = 0.08)
Summary
The Six-minute walk (6MW) and Timed-Up-and-Go (TUG) are short walk tests commonly used to evaluate functional recovery after total knee arthroplasty (TKA). Little is known about walking capacity of TKA recipients over extended periods typical of everyday living and whether these short walk tests predict longer, more functional distances. Little is known about walking ability activity in people with end-stage knee osteoarthritis [13], suggesting that self-reported function tools and timed mobility tests measure different aspects of function [4]. Both forms of assessment are considered necessary post-surgery. It is possible that individuals who appear comparable on a short duration walk test exhibit fatigue and differences in walking endurance beyond six minutes of walking
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