Objectives: This study aimed to evaluate the relationship of leg muscle symmetry to the prevalence, radiographic grade, and symptoms of knee osteoarthritis (OA).
Method: We conducted a cross-sectional study using data from the Korean National Health and Nutrition Examination Survey (KNHANES), collected in 2010 and 2011. Men and women aged 60 years or older were included. Leg muscle mass was measured using dual-energy X-ray absorptiometry, and the muscle asymmetry index was defined as ∣(left leg muscle mass)/(left and right leg muscle mass) × 100 - 50∣. Statistical analyses were performed to examine the relationships between the muscle asymmetry index and the radiographic grade and knee symptoms.
Results: A total of 2548 subjects were included in the analysis. The muscle asymmetry index was positively associated with radiographic knee OA grade and knee pain, especially in men. Men with knee OA and the highest quartile of muscle asymmetry index were 3.3 times more likely to have knee pain compared with those in the lowest quartile. When subjects were divided into four groups by body mass index (BMI) and muscle asymmetry index, subjects with asymmetric obese and men with asymmetric normal BMI had worse grade of radiographic knee OA.
Conclusions: Leg muscle asymmetry in men, irrespective of obesity, was associated with significantly higher grade of radiographic knee OA and prevalent knee pain. Longitudinal studies will be needed to determine the cause-and-effect relationship and to determine whether the higher or lower mass, beyond the asymmetry, is associated with radiographic severity or symptomatic knee OA.Key Points•Leg muscle asymmetry was related to prevalence and radiographic severity of knee OA, especially in men.•Leg muscle asymmetry was associated with knee pain.•Those with both leg muscle asymmetry and obesity showed higher prevalence of knee pain and worse radiographic knee OA.
Keywords: Knee osteoarthritis; Knee pain; Leg muscle; Muscle mass; Muscle symmetry.