An evaluation of pain, pain-related interference, and fatigue among older adults with symptomatic osteoarthritis (OA) of the knee

Fatigue is a common, non-specific symptom often associated with chronic pain and defined as generalized tiredness, weakness, and exhaustion. However, fatigue in osteoarthritis (OA) is not routinely evaluated and has only been considered in few studies to date. Our aim was to evaluate the inter-relationships among pain, pain-related interference, and fatigue as well as whether these factors differed as a function of high versus low OA pain severity. Participants were recruited at the Universities of Alabama-Birmingham and Florida as part of an ongoing study and included 168 individuals (74% female) with symptomatic knee OA. Participants completed the Graded Chronic Pain Scale (GCPS) and were categorized into two pain groups: high (GCPS grades III and IV; N= 101) and low severity (GCPS grades I and II; N= 67). Using telephone-based diaries, participants reported their current pain, pain-related interference, and fatigue across four consecutive weeks. After adjusting for race, gender, BMI and depressive symptoms, multivariate analyses of covariance (MANCOVA) showed that the high pain severity group reported significantly greater current pain (prange = .05 to <.001), pain-related interference (all p’s < .001), and fatigue (prange = .006 to <.001) across all four weekly assessments compared to the low pain severity group. Results also revealed significant correlations among ratings of current pain, pain-related interference, and fatigue across all four weeks within both the high and low pain severity groups. The strength of these correlations was generally greater for the high pain severity group. This study suggests that both OA pain severity and fatigue may be important determinants of pain-related interference. Future research should further address the roles of both pain and fatigue in pain-related interference in OA and address fatigue as a target of comprehensive pain management.