Clinical research provides convincing evidence that total knee arthroplasty (TKA) is safe and improves joint-specific outcomes. However, higher-level functioning associated with self care and independent living has not been studied. Furthermore, most previous studies of the effects of TKA relied on relatively small clinical samples. We undertook this study to estimate the effects of TKA on 3 levels of physical functioning in a national sample of older adults.
Data were obtained from the Medicare Current Beneficiary Survey from 1992 to 2003. Medicare claims data identified participants with osteoarthritis of the knee who received TKA (n=259) or no TKA (n=1,816). Propensity scores were used to match treatment and no-treatment groups according to demographic characteristics, comorbid conditions, and baseline functioning. Three levels of physical functioning were examined as outcomes of TKA. These levels were represented by items on the Nagi Disability Scale, the Instrumental Activities of Daily Living (IADL) Scale, and the Activities of Daily Living (ADL) Scale. These items were measured after TKA and at comparable intervals for the no-treatment group. Average treatment effects were calculated for relevant Nagi Disability Scale, IADL Scale, and ADL Scale tasks.
Between baseline and outcome assessments, TKA recipients improved on all 3 levels of physical functioning; the no-treatment group declined. Statistically significant average treatment effects for TKA were observed for one or more tasks for each measure of physical functioning.
TKA is associated with sizeable improvements in 3 levels of physical functioning among elderly Medicare beneficiaries.