Which matters more for preventing knee replacements: reducing overactivity or combating inactivity?

Daily physical activity (PA) has been gaining attention for the management and prevention of knee osteoarthritis (OA).

This study aimed to compare the effects of various hypothetical daily PA regimens on the incidence of knee replacement (KR) surgery using a targeted learning approach.

We analyzed data from the Osteoarthritis Initiative on adults in the US with symptomatic knee OA or at risk. Daily PA was measured by the Physical Activity Scale for the Elderly (PASE) score. Seven hypothetical daily PA treatment regimens were developed based on the baseline PASE scores. The outcome was the incidence of KR surgery over a 96-month follow-up period. The effects of the PA interventions were estimated using a doubly robust targeted minimum loss-based estimator.

Maintaining the baseline PASE score resulted in a KR surgery incidence ratio of 4.71% (95% CI: 4.37% to 5.05%). Reducing the PASE scores to 200 only for those with scores > 242 decreased the incidence ratio to 2.98% (95% CI: 2.39% to 3.57%). Increasing the PASE scores by 10% and 20% among those with low baseline scores further reduced the risk of KR surgery, whereas increasing them by 30%-50% diminished the additional benefit.

Optimizing daily PA levels, particularly by reducing excessive PA to optimal levels, was beneficial for reducing the risk of KR surgery in older adults with or at risk for knee OA.

Our results suggest that tailoring daily PA to an optimal level is most beneficial.