The Impact of Total Joint Arthroplasty on Long-Term Physical Activity: A Secondary Analysis of the Health and Retirement Study.

OBJECTIVE: Physical inactivity is the fourth leading cause of global mortality and is prevalent among people with lower extremity osteoarthritis. Lower extremity osteoarthritis is the most common arthritis type afflicting older adults, and total joint arthroplasty (TJA) performed to address the condition is Medicare's largest annual expense. Despite TJA intervention to address the disabling effects of osteoarthritis, physical activity (PA) level remains stable 6 months after TJA; however, the effect of TJA on long-term PA $\Big(\ge$2 y) in a representative sample of older adults is unknown. The purpose of this study was to test the hypothesis that PA would remain stable in the long term.

METHODS: In this longitudinal observational study, a probability-weighted difference-in-differences analysis was conducted to observe the predictive margins of nontraumatic hip or knee TJA on levels of vigorous and moderate PA after 2 years. A combined Health and Retirement Study data set of community-dwelling adults who were > 55 years old, had symptomatic osteoarthritis, and were in need of TJA between 2008 and 2018 (N = 4652) was used.

RESULTS: TJA was not associated with vigorous PA ($\updelta$ = 2.37; SE = 5.23) or moderate PA ($\updelta$ = -2.84; SE = 7.76) after 2 years.

CONCLUSION: TJA was not associated with increased long-term PA in older adults with osteoarthritis.

IMPACT: Physical therapists should not assume that there will be a natural increase in PA after functional recovery from TJA procedures. Older adults with lower extremity osteoarthritis may benefit from PA screening and promotion practices in physical therapy services.

LAY SUMMARY: Receiving a total joint replacement does not lead to increased physical activity levels 2 years after surgery.