The impact of momentary pain and fatigue on physical activity in women with osteoarthritis.

OBJECTIVE To examine the daily life patterns of both pain and fatigue symptoms and objective physical activity (using ambulatory monitoring) in women with symptomatic lower extremity osteoarthritis (OA), and to evaluate how momentary symptoms impact physical activity levels. METHODS Sixty women age >or=55 years (40 with knee or hip OA and 20 matched controls) participated in an observational study involving 2 laboratory visits and a 5-day home data collection period. During the home period physical activity levels were assessed continuously, and symptoms were inputted 6 times a day into an enhanced accelerometer at prespecified time points. RESULTS In the OA group as compared with the control group over the 5-day period, average physical activity was significantly lower (P = 0.02) and peak physical activity tended to be lower (P = 0.06). Although pain and fatigue overall were of moderate severity in this cohort, fatigue escalated throughout each day. In a hierarchical linear model, fatigue was most strongly associated with physical activity (beta = -30.1, P < 0.0001). Pain was more weakly associated with physical activity and in the direction opposite to what was hypothesized (beta = 16.9, P = 0.04). CONCLUSION Momentary reports of fatigue negatively predicted physical activity levels and were much more strongly related to physical activity than momentary pain. In order to help women with knee or hip OA manage symptoms and become more physically active, it may be important to emphasize fatigue management.