Comparative responsiveness of locomotor tests and questionnaires used to follow early recovery after total knee arthroplasty.

Objectives: To compare the responsiveness of 3 locomotor tests and 2 questionnaires in the early stage after a total knee arthroplasty (TKA) and to determine if the 4 responsiveness statistics ranked the measures similarly.

Design: Longitudinal study.

Setting: Rehabilitation institute.

Participants: Twenty-five men and 40 women with knee osteoarthritis scheduled for a first TKA.

Interventions: Not applicable.

Main Outcome Measures: Six-minute gait distance, in-laboratory gait speed and stair ascent duration, Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index difficulty subscale, and Medical Outcomes Study Short-Form 36-Item Health Survey role-physical and physical functioning subscale scores. Effect size, standardized response mean, paired t test, and relative efficiency statistics were computed for 3 time intervals: (1) before TKA to 2 months after TKA, (2) 2 to 4 months after TKA, and (3) before TKA to 4 months after TKA.

Results: Responsiveness varied according to tests and intervals considered. For all intervals, the WOMAC difficulty subscale was the most responsive questionnaire and the 6-minute gait test was the most responsive locomotor test. Stair ascent duration was the least responsive measure. Of the responsiveness indices used, only effect size ranked the tests differently.

Conclusions: The 6-minute gait test and the WOMAC difficulty subscale are recommended for outcome assessment during the early recovery period after TKA. Because interpretation guidelines are available and confidence intervals can be calculated for it, the standardized response mean is the most useful statistic.