Objective: To determine the radiographic joint space width (JSW) in undamaged metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of patients with early rheumatoid arthritis (RA) and to identify important clinical determinants of JSW.
Methods: Radiographs of patients with RA of <1 year's duration, from an early arthritis cohort at a tertiary care rheumatology clinic, were obtained. JSW was analyzed by joint, finger, age, sex, height, and a number of other clinically relevant variables. Multivariate analysis was also performed, to account for possible confounding between variables.
Results: Thirty-eight patients were included in the study. We found that JSW was greater in the MCP joint than the PIP joint (P < 0.0001). JSW was significantly greater in men (P < 0.0001) and increased with increasing height (P < 0.003), but was not associated with age (P < 0.21). In multivariate analyses, sex was shown to be the most important predictor of JSW.
Conclusion: In patients with early RA, MCP and PIP JSW is significantly associated with sex and height. In studies of RA in which JSW measurements are included as an outcome, these differences may need to be accounted for in the analysis.