Association of Muscle Quality and Pain in Adults With Symptomatic Knee Osteoarthritis, Independent of Muscle Strength: Findings From a Cross‐Sectional Study

Abstract

ObjectiveKnee osteoarthritis (OA) is a leading cause of chronic pain in adults and shows wide inter‐individual variability, with peripheral and central factors contributing to the pain experience. Periarticular factors such as muscle quality (e.g., echo intensity and shear wave velocity) may contribute to knee OA pain; however, the role of muscle quality in OA symptoms has yet to be fully established.MethodsTwenty‐six adults (age > 50 years) meeting clinical criteria for knee OA were included in this cross‐sectional study. Quantitative ultrasound imaging was used to quantify echo intensity and shear wave velocity in the rectus femoris of the index leg. Pearson correlations followed by multiple linear regression was used to determine associations between muscle quality and pain, controlling for strength, age, sex, and body mass index (BMI).ResultsEcho intensity and shear wave velocity were significantly associated with movement‐evoked pain (b's=0.452‐0.839, p's=0.024‐0.029). Clinical pain intensity was significantly associated with shear wave velocity (b=0.45, p=0.034), as were pressure pain thresholds at the medial (b=‐0.41, p=0.025) and lateral (b=‐0.54, p=0.009) index knee joint line, adjusting for all covariates. Pain interference was significantly associated with knee extension strength (b=‐0.51, p=0.041).ConclusionThese preliminary findings suggest that echo intensity and shear wave velocity may impact knee OA pain and could serve as malleable treatment targets. Findings also demonstrate that muscle quality is a unique construct, distinct from muscle strength, which may impact pain and treatment outcomes. More research is needed to fully understand the role of muscle quality in knee OA.