Ultrasonographic assessment of quadriceps muscle in people with knee osteoarthritis: A systematic review and meta-analysis

Knee osteoarthritis (OA) is a painful joint condition characterized by changes in quadriceps femoris muscle architecture and quality. Although ultrasound is an emerging tool for evaluating muscle conditions in this population, its usefulness and clinical implications remain unclear. To investigate the effects of knee OA on quadriceps muscle architecture, summarize ultrasound protocols used in studies, and explore the associations between muscle characteristics with symptoms and physical function. Searches across 3 electronic databases (PubMed, PEDro, and EMBASE) were performed by 2 independent investigators according to strict inclusion and exclusion criteria. The findings highlight that ultrasound protocols often lack detailed descriptions, even if there is growing interest in how the quadriceps femoris muscle changes in knee osteoarthritis people, particularly in muscle thickness and echo intensity. The meta-analysis revealed that vastus medialis muscle thickness was significantly lower in individuals with knee OA compared to healthy controls (mean difference:0.52 mm; 95 % CI -1.01 to -0.03; P = 0.037), whereas no significant differences were found for rectus femoris, vastus lateralis, or vastus intermedius thickness. In the qualitative synthesis, the systematic literature analysis showed muscle changes, including a decreased muscle quality in both the vastus medialis and vastus intermedius. Additionally, quadriceps femoris muscle thickness is associated with condition-specific, patient-reported outcomes and functional performance in people with knee OA, whereas there is a relationship between echo intensity and functional performance. The study highlights the need for standardized ultrasound protocols to capture changes in quadriceps muscle architecture and quality, as some of these changes correlated to patient-reported outcomes measures and functional performance in knee OA people. Finally, we propose a recommendation to improve the measurement of muscle echo intensity in clinical practice. PROSPERO database (registration number: CRD42023471617).