Differences in health-related quality of life among subjects with frequent bilateral or unilateral knee pain: data from the Osteoarthritis Initiative study.

STUDY DESIGN Cross-sectional study. OBJECTIVE To examine associations between frequent bilateral knee pain (BKP) and unilateral knee pain (UKP) and health-related quality of life (QoL). We hypothesized that frequent BKP would be associated with poorer health-related QoL than would frequent UKP and no knee pain. BACKGROUND Knee pain is one of the most frequently reported types of joint pain among adults in the United States. It is the most frequent cause of limited physical function, disability, and reduced QoL. METHODS Data were collected from the Osteoarthritis Initiative public-use data sets. Health-related QoL was assessed in 2481 participants (aged 45-79 years at baseline). The Knee injury and Osteoarthritis Outcome Score QoL subscale (knee-specific measure) and the physical component summary and mental component summary (MCS) scores of the Medical Outcomes Study 12-Item Short-Form Health Survey (SF-12) (generic measure) were used to assess health-related QoL. Multiple regression analyses were used to examine the relationships between frequent knee pain and health-related QoL, adjusted for sociodemographic and health covariates. RESULTS Compared with subjects with no knee pain, subjects with frequent BKP and UKP had significantly lower scores on the Knee injury and Osteoarthritis Outcome Score QoL subscale (mean difference, -35.2; standard error [SE], 0.86; P<.001 and mean difference, -29.2; SE, 0.93; P<.001; respectively) and the SF-12 physical component summary score (mean difference, -6.25; SE, 0.41; P<.001 and mean difference, -4.10; SE, 0.43; P<.001; respectively), after controlling for sociodemographic and health covariates. The SF-12 MCS score was lower among those with BKP (-1.29; SE, 0.42; P<.001). Frequent UKP was not associated with the SF-12 MCS. CONCLUSION Subjects with frequent BKP had lower health-related QoL than those with frequent unilateral or no knee pain, as reflected in lower Knee injury and Osteoarthritis Outcome Score QoL subscale and SF-12 physical component summary and MCS scores.