Rheumatoid arthritis and knee joint deformity are serious conditions that may require joint replacement surgery. For less serious cases, non-steroidal anti-inflammatory drugs, such as etoricoxib or celecoxib, are generally used to treat and alleviate symptoms. The onset of rheumatoid arthritis is associated with streptococcal infections. Clinically, joint deformities are rare, so if joint deformity occurs, it is important to investigate the possibility of rheumatoid arthritis. Since rheumatoid arthritis is an immune-mediated erosive arthritis that can lead to bone destruction and joint deformity, rheumatoid factor and anti-CCP antibodies can be tested for diagnostic differentiation.