ACR: American College of Rheumatology; AAHKS: American Association of Hip and Knee Surgery; MTX: methotrexate; DMARDs: disease-modifying anti-rheumatic drugs; RA: rheumatoid arthritis; TNF-α: tumor necrosis factor alpha; pre-op: preoperative; SLE: systemic lupus erythematosus. Here, TNF is linked to rheumatoid arthritis.