To assess and compare the impact of total knee arthroplasty (TKA) in patients with rheumatoid arthritis (RA) and patients with osteoarthritis (OA).
Patients with rheumatologist-diagnosed arthritis undergoing primary TKA during 1999-2012 were identified. Indices of pain (overall, index knee, and contralateral knee) and health-related quality of life (HRQOL) were obtained in 3 consecutive 6-month intervals: preoperative (baseline), perioperative, and postoperative (recovery). Descriptive statistics and one-way analysis of variance were used to compare TKA outcomes by diagnosis. Effect sizes and standardized response means (SRMs) were calculated between baseline and recovery.
Of the participating 18,897 patients, 834 of those with RA (5.3%) and 315 of those with OA (10.2%) had undergone index TKA at similar mean ages (65 and 68 years). Post-TKA, significant improvements were observed for most domains of pain, function, and HRQOL within both disease groups, with greater impact in OA. Based on the SRM, the maximum improvement was shown in index knee pain (SRM -1.33 in RA and -1.34 in OA; effect size -1.75 and -1.94, respectively). The Health Assessment Questionnaire II and the Short Form 36 physical component summary were the most responsive HRQOL indices in detecting post-TKA improvement in RA. A diagnosis of RA, lower income, and preoperative anxiety were independently associated with a lower degree of improvement in index knee pain following TKA.
TKA is highly effective in reducing clinically relevant knee pain (to a greater extent than its effect on other subjective HRQOL indices in patients with RA), although this improvement is less marked as compared to that among patients with OA. TKA serves as a "time machine" via which patients can return to a lifestyle with less disability, before the arthritis process catches up in RA.