Symptomatic knee osteoarthritis is associated with worse but stable quality of life and physical function regardless of the compartmental involvement: Data from the OAI

To test whether combined patellofemoral and tibiofemoral osteoarthritis (OA), in addition to symptoms, is associated with greater changes in quality of life and objective physical function measures when compared with asymptomatic isolated tibiofemoral osteoarthritis. Of the 4796 participants in the Osteoarthritis Initiative, 577 were categorized into four groups based on the presence of symptoms (asymptomatic and symptomatic) and the structural involvement within the knee, where tibiofemoral OA was graded with the Kellgren and Lawrence scale, while patellofemoral OA was based on the Magnetic Resonance Imaging Osteoarthritis Knee Scoring cartilage loss feature. Knee-related quality of life was examined using the Knee Injury and Osteoarthritis Outcome Scale quality of life subscale, and objective physical function was examined by the 20 m Walk Test, 30-s Chair Stand Test, and isometric knee strength. These outcomes were measured at Baseline, Year 2, and Year 4. Mixed effects models were fit to test whether the change in outcome, and the Baseline scores, differed based on group. Quality of life worsened for the asymptomatic combined group but improved for the symptomatic combined group. However, these quality of life changes and changes in other outcomes were all within measurement error. Large between-group differences were found at Baseline, whereby individuals with symptoms had worse quality of life and physical function test scores. Quality of life and physical function are largely stable over four years. However, having symptoms is strongly associated with worse quality of life and physical function, regardless of structural disease distribution within the knee.