*2.1. Patients*

A total of 14 patients with long-standing RA fulfilling the American College of Rheumatology revised criteria for RA [40] were included in this study. The RA group comprised of 14 females with a mean age of 68 years ± 10 years. C-reactive protein was 7.1 mg/dL± 9.2 mg/dL 3 out of 14 glucocorticoids, 4 out of 14 methotrexate, 1 out of 14 sulfasalazine, 3 out of 14 biologicals and 1 out of 14 JAK inhibitor. All patients underwent elective knee joint replacement surgery, and they were informed about the purpose of the study and gave written consent. The study was approved by the Ethics Committees of the University of Düsseldorf (approval numbers 2018-87-KFogU and 2018-296-KFogU). We confirm that all experiments were performed in accordance with relevant guidelines and regulations.
