Replacing Stationary and Physical Activity Time Is Associated With 2-Year Improvements in Clinical Outcomes in...

The purpose of this study was to investigate the longitudinal association of replacing stationary time (ST) with either light (LPA) or moderate-to-vigorous (MVPA) physical activity and replacing LPA with MVPA on 2-year clinical outcomes in individuals with varying severities of knee osteoarthritis.

This retrospective cohort study used isotemporal substitution models to investigate the association of replacing 10-60 min of ST with LPA or MVPA and of LPA with MVPA on Western Ontario and McMaster Universities Osteoarthritis Index pain, stiffness, function, and gait speed at 2 years. Device-based stationary and physical activities were monitored using accelerometry within the Osteoarthritis Initiative cohort (n = 848). All analyses were completed separately for mild-to-moderate (Kellgren-Lawrence grade = 1-2) and severe (Kellgren-Lawrence grade = 3-4) knee osteoarthritis groups.

In individuals with mild-to-moderate osteoarthritis, substituting 30-60 min of ST or LPA with MVPA improved pain and gait speed at 2 years but worsened stiffness. Replacing 60 min of ST with LPA improved Western Ontario and McMaster Universities Osteoarthritis Index function. For severe osteoarthritis, substituting 30-60 min of ST or LPA with MVPA led to worsened Western Ontario and McMaster Universities Osteoarthritis Index pain and function at 2 years, whereas substituting ST or LPA with MVPA minimally impacted stiffness. Improvements in gait speed were observed with 10-to-60-min ST or LPA substitutions with MVPA.

Stationary and physical activity substitutions had varying longitudinal effects in individuals with mild-to-moderate versus severe knee osteoarthritis. Individuals with mild-to-moderate and severe knee osteoarthritis may require differing physical activity prescription to improve functional and overall health outcomes. Significance/Implications: These findings underscore the importance of severity-specific physical activity recommendations to support clinical outcomes in knee osteoarthritis management.