Associations of Coexisting Pain and Fatigue Severity with Physical Performance and Quality of Life among Middle-Aged and Older Individuals with Chronic Knee Pain: A randomized controlled trial
Abstract Objective To examine associations of combined pain and fatigue severity with physical performance and quality of life in people with chronic knee pain. Design Cross-sectional. Setting General community. Participants Adults (N = 193) aged ≥ 50 years with chronic knee pain. Methods Physical performance measures included Six-Minute Walk test, Timed Up and Go test, and 20-feet timed walk test. Quality of life (QOL) was measured by the Medical Outcomes Study Short Form-12 Health Survey. Brief Pain Inventory (BPI) and Brief Fatigue Inventory (BFI) were used to evaluate pain and fatigue. Multiple linear regression analyses were conducted to examine associations of coexisting pain and fatigue severity with physical performance and quality of life. Results Based on BPI and BFI scores, participants were categorized into four severity groups: mild pain/fatigue; moderate pain/mild fatigue; mild pain/moderate fatigue; and moderate pain/fatigue (which included severe pain/fatigue). The moderate pain/fatigue group had significantly worse physical performance on Six Minute Walk (standardized beta (β) = − 0.22, 95% confidence interval (CI) [-.38, -.06], P < 0.05), poorer physical (β = − 0.41, 95% CI [-.61, -.20], P < 0.001) and mental QOL (β = − 0.26, 95% CI [-.46, -.07], P < 0.05) compared to the mild pain/fatigue group. Moreover, the mild pain/moderate fatigue group had significantly lower levels of mental QOL (β = − 0.27, 95% CI [-.44, -.10], P < 0.05) when compared to the mild pain/fatigue group. The moderate pain/mild fatigue group did not differ statistically compared to the mild pain/fatigue group. Conclusions Coexisting moderate pain and moderate fatigue were related to worse physical performance and QOL. Fatigue contributed to lower levels of mental QOL. Clinical assessment of fatigue in addition to pain should be included as a standard examination for chronic knee pain.