Three Distinct Step Count Trajectories Identified at 3-Months After Total Knee Replacement: An Exploratory Cohort Study

OBJECTIVE: To determine if participants demonstrate distinct trajectories of step count following total knee replacement, and whether their baseline characteristics differ. DESIGN: Longitudinal repeated measures study within a randomized-controlled trial. METHODS: Participants were recruited from 3 hospitals in Sydney, Australia. Only participant data from the intervention group were used for this study (n = 51). Baseline data including demographics, pain (0-10 numerical rating scale), 13-item Patient Activation Measure scale, and modified Computer Self-efficacy Scale were collected. Participants received an activity tracker to monitor daily step counts. Latent class analyses were used to identify distinct trajectories of step count from baseline to 3-month follow-up. Baseline characteristics were compared using multinomial logistic regression. RESULTS: 43 participants were included in the analysis. Participants were predominantly female (n = 30, 70%) with an average age (SD) of 67.7 (7.5) years and body mass index (SD) of 30.3 (6.0). Three distinct step count trajectories were identified: a “high and rapidly increasing” group (n = 6, 14%), who began at 6251 ± 3508 steps and achieved 12794 ± 3173 steps by weeks 9 to 11; a “low and gradually increasing” (n = 24, 56%), (baseline: 2843 ± 1058 steps, 12 weeks: 6441 ± 1677 steps) ; and “high and gradually increasing” (n = 13, 30%), (baseline: 6299 ± 1777 steps, 12 weeks: 9614 ± 1436 steps). At baseline, body mass index and pain significantly differed between groups. CONCLUSION: Three distinct step count trajectories were found in people with total knee replacement. Findings highlight the variability between patient groups and the need for support for those who may not be reaching prescribed step goals. JOSPT Open 2023;1(1):78-85. Epub 11 August 2023. doi:10.2519/josptopen.2023.0011