To clarify the influence of individual joint impairment on functional capacity through a retrospective study with a 3-year interval, using a large cohort of Japanese patients with rheumatoid arthritis (RA).
Subjects included 3457 patients with RA who participated in a large observational cohort study in both April 2004 and April 2007; 43 joints were assessed and classified into 10 joint areas. Impairment of each joint area was scored based on the presence of swelling or tenderness: score 0 (no swelling or tenderness in either joint), score 1 (swelling or tenderness in a unilateral joint), and score 2 (swelling or tenderness in bilateral joints). Score change was defined as the difference between scores from 2004 and 2007. The Japanese validated version of the Health Assessment Questionnaire is the J-HAQ; ΔJ-HAQ score was determined by subtracting J-HAQ score in 2007 from that in 2004. The relationship between score change and ΔJ-HAQ score, and the effect of joint impairment on ΔJ-HAQ score were assessed.
Major joint areas that contributed to ΔJ-HAQ score included the wrist (31%), shoulder (21%), knee (13%), and ankle (10%). The shoulder, wrist, knee, and ankle in the worsening group were associated with a J-HAQ score increase of 0.13 to 0.18 compared to the improvement group.
Our study demonstrated that impairment of the shoulder, wrist, knee, and ankle significantly affects functional capacity in patients with RA. Care of these joints is suggested to be especially important for better functional outcomes.