Changes in knee joint destruction patterns among patients with rheumatoid arthritis undergoing total knee arthroplasty in recent decades

OBJECTIVES: This study aimed to investigate the trend of joint destruction patterns on knee radiographs of patients with rheumatoid arthritis (RA) undergoing total knee arthroplasty (TKA) over the past 16 years. METHOD: Medial joint space, lateral joint space, medial spur area, lateral spur area (L-spur), and femoro-tibial angle were obtained from 831 preoperative knee radiographs of patients with RA who underwent TKA between 2006 and 2021 using software capable of automatic measurements. Non-hierarchical clustering was performed based on these five parameters. Trends in the five individual radiographic parameters and the ratio of each cluster were investigated during the target period. Moreover, clinical data from 244 cases were compared among clusters to identify factors associated with this trend. RESULTS: All parameters, except for L-spur, showed significant increasing trends from 2006 to 2021. The radiographs were clustered into groups according to the characteristic pattern of radiographic findings: cluster 1 (conventional RA type), with bicompartmental joint space narrowing (JSN), less spur formation, and valgus alignment; cluster 2 (osteoarthritis type), with medial JSN, medial osteophytes, and varus alignment; and cluster 3 (less destructive type), with mild bicompartmental JSN, less spur formation, and valgus alignment. The ratio of cluster 1 showed a significantly decreasing trend contrary to the significantly increasing trend in clusters 2 and 3. The DAS28-CRP of cluster 3 was higher than those of clusters 1 and 2. CONCLUSIONS: Radiographs of TKA recipients with RA are increasingly presenting osteoarthritic features in recent decades.