Multisite Musculoskeletal Pain Is Associated with Long-Term Declined Physical Quality of Life and Knee-Related Quality of Life in Older Adults with or at Risk of Knee Osteoarthritis

<i>Background and Objectives</i>: This study aimed to examine the longitudinal impact of multisite musculoskeletal pain on physical and mental health-related quality of life among individuals with or at risk of knee osteoarthritis. <i>Materials and Methods</i>: This study is a prospective longitudinal design over 8 years of follow-up. Data from 4796 participants aged between 45 and 79 years were acquired from the Osteoarthritis Initiative. Based on self-reported physician-diagnosed osteoarthritis and grade ≥2 in either knee using Kellgren and Lawrence grade at baseline, individuals at risk were classified as those who did not have knee osteoarthritis at baseline but could develop osteoarthritis throughout the study. Physical and mental components of health-related quality were assessed over an 8-year follow-up period using both knee injury and osteoarthritis outcome scores and the 12-item Short-Form Health Survey. Multisite pain was examined using a self-reported questionnaire for 20 sites. Two separate generalized estimating equations modeled with a linear regression analysis were utilized. <i>Results</i>: The results showed that participants with one painful site (Beta [B] = -0.92, <i>p</i> = 0.01), two painful sites (B = -1.94, <i>p</i> < 0.001), and multisite pain (≥3 painful sites) (B = -4.68, <i>p</i> < 0.001) were significantly associated with declined physical health-related quality of life over time when compared to those with no painful site at baseline after adjustments for covariates. However, there was no significant association with declined mental health-related quality of life over time. <i>Conclusions</i>: This study revealed that baseline multisite musculoskeletal pain was linked to declining physical and knee injury and osteoarthritis outcome score quality of life among individuals with or at risk of knee osteoarthritis. Moreover, having baseline multisite pain and two painful sites were associated with a decline in physical and knee injury and osteoarthritis outcome score quality of life, while mental health-related quality of life did not show a significant association with multisite pain. Therefore, it is imperative for primary healthcare settings to prioritize the assessment of multisite musculoskeletal pain and develop interventions aimed at preserving and enhancing physical health-related quality of life in people with or at risk of osteoarthritis.