Background/Purpose: Following total knee replacement rehabilitation, patients are advised to participate in physical activity. Yet, most individuals at this stage do not increase their physical activity levels despite the known health benefits and improvements in objective knee outcomes. In addition to providing physical rehabilitation to patients following total knee replacement, physical therapists are often utilized as promoters of physical activity. To ensure all patients are attaining the recommended guidelines on physical activity post-operatively, physical therapists need to be able to identify those individuals at a higher risk of low physical activity at the start of outpatient therapy. Furthermore, it is unclear if there are identifiable demographic or socioeconomic factors that contribute to physical activity levels 12 weeks after surgery. Therefore, the purpose of this study was to determine whether these factors can predict moderate-to-vigorous physical activity (MVPA) at 12 weeks after surgery.

Methods: Adults aged 48-79 years from the PATH study, a 12-week randomized clinical trial promoting physical activity after knee replacement through outpatient physical therapy were included in this analysis. Participants were randomized to physical activity counseling throughout outpatient physical therapy or standard outpatient physical therapy. All participants wore an ActiGraph GT9x Link (ActiGraph, Pensacola, FL) accelerometer for a period of 7 days at baseline and 12 weeks after surgery. Total minutes of MVPA (≥2020 counts/min) per week were calculated among participants with >4 valid days (≥10 hours of wear time). Multiple linear regression was used to identify associations between sex, age, annual household income, total number of comorbidities and total minutes of MVPA at 12 weeks.

Results: A total of 38 participants were included in the analysis (57.8% female, 71% white, 65.4 ± 7.3 years, body mass index 32.4 ± 6.5 kg/m²). Participants averaged 6.3 ± 1.0 valid accelerometer wear days and had a mean 52.7 ± 58.4 minutes/week of MVPA, with no differences between randomized conditions. The overall regression significantly predicted total time of minutes of MVPA at 12 weeks, F(4, 33) = 9.607, p < 0.001, R² = .538. Women (β= -38.997, p < .05), adults of older age (β=-2.599, p < .05), and those with a higher number of comorbidities (β= -8.215, p = .066) were associated with decreased MVPA at 12 weeks after knee replacement. Conversely, a higher annual household income (β= 12.319, p < .05) was linked with more MVPA.

Conclusion: Lower levels of MVPA at 12 weeks after total knee replacement were found among women, adults of older age, those with lower annual household incomes, and a higher number of comorbidities. Physical therapists should incorporate additional strategies to overcome barriers at the start of outpatient therapy that might prevent knee replacement patients reflective of these socioeconomic and demographic factors from obtaining recommended levels of MVPA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/predictors-of-moderate-vigorous-physical-activity-following-a-physical-therapist-led-physical-activity-intervention-for-adults-with-total-knee-replacement/