Diurnal variation of gait in patients with rheumatoid arthritis: The DIVIGN study☆

BACKGROUND Circadian variation of joint stiffness (morning stiffness) and its impact on functional ability are widely recognised in rheumatoid arthritis. Subsequent within-day variation of walking ability is important due to the increased availability of instrumented gait analysis. This study aimed to quantify diurnal variation of gait in patients with rheumatoid arthritis, and explore associations with disease characteristics. METHODS Thirty one inpatients with rheumatoid arthritis walked at a self-selected speed along a GAITRite instrumented walkway 5 times during a single day. FINDINGS Participants showed marked diurnal variation in gait, leading to a systematic variation throughout the day (F=19.56, P=<0.001). Gait velocity and stride length both increased, whereas the proportion of each gait cycle spent in stance phase or double support decreased, consistent with improving function throughout the day. Although absolute gait velocity correlated with disease characteristics, the magnitude of diurnal variation appeared to be independent of disease activity (rho=0.26, P=0.15), disease duration (rho=-0.19, P=0.324), and underlying functional ability (rho=0.09, P=0.65). INTERPRETATION Although morning stiffness is well recognised in rheumatoid arthritis, this is the first time that its effect on gait has been quantified. Patients with rheumatoid arthritis exhibited a systematic change in walking ability throughout the day, which was independent of disease characteristics. These findings have important implications for the interpretation of existing data and the design of future studies. Repeat measures should be conducted at the same time of day to exclude the effects of diurnal variation.