To evaluate the associations between sex, age, body mass index (BMI) and handedness regarding the radiogeometric detectable joint space distances of the finger articulations in patients suffering from a prolonged course of rheumatoid arthritis (RA). The joint space widths were measured by a new available Computer-aided joint space analysis (CAJSA); 128 patients with RA underwent computerized semi-automated joint space analysis of joint space distances at the metacarpal-phalangeal articulation (JSD-MCP II-V), proximal-interphalangeal joint (JSD-PIP II-V) and distal-interphalangeal joint (JSD-DIP II-V) based on digitally performed radiographs of the hand (Radiogrammetry Kit, Version 1.3.6; Sectra; Sweden). The joint space distance (JSD) of each articulation was expressed as JSD total in millimeter. The patient cohort was differentiated for gender, age, handedness and BMI (BMI < 20; BMI 20-25, BMI > 25). JSD revealed a significant age-related narrowing of 24.8% (JSD-MCP), 22.6% (JSD-PIP) and 28.7% (JSD-DIP) between the ages of 20 and 79. Additionally, males showed a significantly wider JSD compared to the female cohort for all age groups. All JSD-distances were varied between the right and left hand. The JSD-MCP demonstrated significant differences regarding the BMI groups. In contrast to JSD-MCP an effect of the BMI on measurements of JSD-PIP and JSD-DIP could not be observed. These influences must be differentiated from disease-related alterations caused by RA.