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

Abstract

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.

Keywords: cross-sectional study; knee joint; pain; quality of life.

FIGURE 1

Flow diagram of selection and classification of subjects enrolled in the Osteoarthritis Initiative study that was included in the present study. ^*The Osteoarthritis Initiative Study has made large, heterogeneous data sets available for public use (http://oai.epi-ucsf.org/datarelease/). ^†Subjects with symptomatic tibiofemoral knee osteoarthritis at baseline. ^‡Subjects with no symptomatic tibiofemoral osteoarthritis in either knee at baseline. ^§Subjects with no pain, aching, or stiffness in either knee in the past year; no radiographic finding of osteoarthritis; and no eligibility risk factors. ^lInfrequent pain in one knee and no pain in the other knee or infrequent pain in both knees. ^¶Data missing for the variable indicating which knee was eligible for the study. ^#Frequent pain in both knees. ^**Frequent pain in one knee, no pain in the other knee. ^††No pain in either knee.

FIGURE 2

Scores reflecting health-related quality of life among subjects with frequent bilateral knee pain, frequent unilateral knee pain, and no knee pain. Abbreviations: KOOS, Knee Injury and Osteoarthritis Outcome Score; MCS, mental component summary score of the Medical Outcomes Study 12-Item Short-Form Health Survey; PCS, physical component summary score of the Medical Outcomes Study 12-Item Short-Form Health Survey; QoL, quality of life.