Changes in Functional Status Among Persons Over Age Sixty-Five Undergoing Total Knee Arthroplasty

Background: This study assessed changes in physical functional status following receipt of total knee arthroplasty (TKA) for patients diagnosed with osteoarthritis (OA) of the knee in a national sample of persons aged 65+ in the United States relative to a sample of similar OA patients who did not receive TKA. Methods: Data from the Health Retirement Survey (HRS) and linked Medicare claims from 1994 to 2006 were used to identify persons with diagnoses of OA of the lower leg who received a TKA (n = 516) and those who did not receive TKA (n = 1756). Predicted probabilities of receiving total knee arthroplasty from logit analysis were used for matching TKA and comparison groups on demographic, socioeconomic, and baseline functional status factors. Functional status measures were: mobility, gross motor function, large muscle, and limitations in activities of daily living (ADL). Average treatment effects of the treated (ATT), which compares changes in functional status between those who received TKA with similar individuals who did not receive TKA, were computed using propensity score matching. Results: Mobility (average treatment effect of the treated (ATT 0.315; 95% Cl: 0.118-0.512), gross motor function (ATT = 0.314; 95% Cl: 0.156-0.472), and ADL limitations (ATT = 0.174; 95% Cl: 0.055-0.293), improved among persons receiving TKA relative to the comparison group. Relative to the mean values of the physical function at baseline, mobility, gross motor function, and ADL limitations persons receiving TKA had better functional outcomes than the comparison group by 17.5, 39.3, and 46.9 percent, respectively. Conclusions: TKA is effective in improving functional status in elderly persons,