Abstract
Knee osteoarthritis (OA) is a complex condition involving articular cartilage, connective tissue, and skeletal muscle. Diagnostic ultrasound (US) has been proposed as an approach to characterize muscle changes in those with chronic conditions. The purpose of this study was to determine if quantitative US muscle morphology and morphometry measures are associated with clinical markers of knee OA. Male Veterans with knee OA (n=36; age=62.2 ± 5.7 yr; BMI=31.2 ± 6.5) participated in the study. Self-reported symptoms and physical function were evaluated using the Knee injury and Osteoarthritis Outcome Score (KOOS). Knee OA asymmetry was determined by the Kellgren–Lawrence grade and self-reported pain. B-mode quantitative US with a 13–6 MHz linear array transducer was used to obtain tissue echogenicity and muscle thickness values. The primary scanning site was the rectus femoris. Additional sites at the trapezius, deltoid, pectoralis major, and brachioradialis were used as proxy measures of lean body mass (LBM). Lower echogenicity (△ -3.04 grayscale levels, t=2.70, p=.01) and greater muscle thickness (△ .17 cm, t=2.21, p=.03) of the rectus femoris were identified in the less involved limb. Additionally, the summed US muscle thickness values were associated with the Symptom and Sports/Recreation KOOS subscales (r=.37–.39, p=.02–.03), and the deltoid was the only muscle group associated with all 5 KOOS subscales (r=.36–.45, p=.01–.04). In summary, US-derived muscle morphology and morphometry measures identified knee OA asymmetries in Veteran men. Key upper extremity muscle groups and proxy estimates of LBM should not be overlooked as factors that affect the KOOS score.