Muscle strength is the main associated factor of physical performance in older adults with knee osteoarthritis regardless of radiographic severity

The aim of the study is to compare factors associated with physical performance in older individuals with severe knee osteoarthritis and those with less-severe osteoarthritis. This is an ancillary cross-sectional study to a population-based cohort study focusing on Koreans age 65 years or older. The analysis included 553 subjects with information about knee pain, depressive symptoms, and comorbidities collected by self-reported questionnaire, and body weight, knee osteoarthritis severity, muscle strength, and physical measures by observer-rated tests. Stepwise logistic regression analyses were performed with physical performance as an outcome variable and the others as independent variables across radiographic knee osteoarthritis severity. In the minimal-to-moderate-severity group, muscle strength, knee pain, BMI, and age were related to poor performance (OR [CI] 0.81 [0.73–0.90], 1.12 [1.03–1.21], 0.87 [0.79–0.96], and 1.09 [1.05–1.14], respectively). In the severe group, muscle strength was the only factor significantly associated with poor performance (OR [CI] 0.72 [0.58–0.89]). Muscle strength, knee pain, and BMI were important determinants of physical performance in the older population with knee osteoarthritis. In severe knee osteoarthritis patients, muscle strength was the only significant determinant.