Validity and Responsiveness of Floor Sitting-Rising Test in Post–Total Knee Arthroplasty: A Cohort Study

Abstract

ObjectivesTo assess the construct validity and responsiveness of the floor sitting-rising test (SRT) in individuals with total knee arthroplasty (TKA). DesignCohort study with 6-month follow-up. Secondary analysis using data from a randomized controlled trial. SettingAn outpatient rehabilitation research center. ParticipantsParticipants (N=240) enrolled in the parent study who had unilateral primary TKA. InterventionParticipants in the parent study underwent 12 weeks of exercise programs. Main Outcome MeasuresValidity analysis correlated baseline data of participants who completed the SRT and measures of knee motion, muscle strength, performance-based tests, and patient-reported outcomes of physical and psychosocial function. Responsiveness analysis used the 3- and 6-month follow-up data. Effect sizes were calculated using changes from baseline. Areas under the receiving operating characteristics curve were calculated using a global rating of change as the external anchor. ResultsOf the 240 participants (148 women; age, 70±7y), 180 (75%) were able to perform the SRT at baseline. Performers scored significantly better in all physical function tests (P<.0001) than nonperformers. SRT scores generally converged with measures of knee impairment and performance-based tests (associations ranged from small [r=0.15; P=.0516] to moderate [r=0.52; P<.0001]). SRT scores associated with self-efficacy for function (r=0.34; P<.0001) and fear of falls (r=-0.25; P=.001). At 3 (n=174) and 6 months (n=160), SRT effect sizes were 0.38 (95% confidence interval, 0.25-0.52) and 0.42 (95% confidence interval, 0.25-0.60), and areas under the curve were 0.59 (95% confidence interval, 0.49-0.69) and 0.62 (95% confidence interval, 0.52-0.73), respectively. ConclusionsThe results add evidence to the validity of the SRT in patients after TKA. The strength of the associations suggests that the SRT measures a physical function construct not captured by the other tests. The magnitude of indices of responsiveness for the SRT were similar to other performance-based tests, indicating comparable responsiveness to more widespread tests of functional performance.