[Recovery of knee function after total knee arthroplasty: different outcomes in patients with osteoarthritis and rheumatoid arthritis]. / Gelenkfunktion nach bikondylärer Knieendoprothese: Unterschiedlicher Verlauf bei Patienten mit Gonarthrose und rheumatoider Arthritis.

INTRODUCTION: Following total knee arthroplasty (TKA), no investigations have been published to assess possible differences between rheumatoid arthritic (RA) and osteoarthritic (OA) patients with respect to patient-reported outcome measures of knee function. PATIENTS AND METHODS: A cohort of 128 consecutively operated patients (OA: n = 92, RA: n = 36) treated with bicondylar TKA was included in this prospective, clinical study. Knee function was assessed preoperatively and at 6 and 12 months after TKA, using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Oxford Knee Score (OKS). RESULTS: Both OKS and KOOS revealed a statistically significant improvement for OA and RA patients at 6 and 12 months after surgery, as compared to the preoperative status. The results of the OKS at 6 and 12 months did not show a further improvement for either group. The KOOS, however, revealed an additional improvement between 6 and 12 months for the osteoarthritis group, regarding the total score and all subscores, but not for the RA subgroup. CONCLUSION: Functional recovery after TKA improves in the second 6 months after surgery in OA patients, but not in RA patients, when knee function is exclusively assessed with patient-reported outcome measures.