Moderate-To-Vigorous Physical Activity Independent of Stationary Time Is Associated With Better Functional Outcomes Over Four-Years in Individuals With or at Risk of Knee Osteoarthritis.

INTRODUCTION: Osteoarthritis is a progressive joint disease that causes pain and disability, impairing physical function. Moderate-to-vigorous physical activity (MVPA) is recommended for knee osteoarthritis, while stationary time, independent of activity, may negatively impact health outcomes. We hypothesised that individuals with the highest MVPA and lowest stationary time would have better long-term function compared to those with the lowest MVPA and highest stationary time, as well as those with high levels of both MVPA and stationary time.

METHODS: Data included 442 participants, with an average age of 66-years and 190-females from the Osteoarthritis Initiative who wore accelerometers to assess MVPA and stationary time. Participants were grouped into tertiles of MVPA and stationary time normalised to total accelerometer wear time. The three groups were: highest activity, lowest stationary (HALS), highest activity, highest stationary (HAHS), and lowest activity, highest stationary (LAHS). Gait speed, the 400 m walk test, and five-time repeated chair stand were assessed at baseline and four-year follow-up.

RESULTS: Compared to the LAHS group, the HALS and HAHS groups had better performance in gait speed p < 0.001, d = 0.96-1.06, 400m walk time p < 0.001, d = 1.21-1.36, and five-time repeated chair stand p < 0.001, d = 0.54-0.81 at baseline and four-year follow-up. No differences were found between the HALS and HAHS groups at either timepoint.

CONCLUSION: Higher levels of MVPA were associated with better lower-limb functional outcomes in individuals with or at risk of knee osteoarthritis. Higher levels of stationary time do not negatively influence functional performance as long as higher numbers of MVPA levels (∼30 min/day) are achieved.