Quantitative ultrasound assessment of gastrocnemius muscle changes in patients with knee osteoarthritis

Background Knee osteoarthritis presents with posterior knee pain, stiffness, and restricted mobility, potentially affecting periarticular muscle biomechanics. We ultrasonographically assessed the gastrocnemius medialis properties in patients with knee osteoarthritis compared with those in healthy controls. Methods This study comprised 76 participants divided into symptomatic patients with knee osteoarthritis and gastrocnemius medialis involvement and healthy controls. Gastrocnemius medialis morphology (thickness and pennation angle) was evaluated using conventional ultrasound, whereas shear touch elastography was applied to assess tissue stiffness via elasticity (Gmean). Results Gastrocnemius medialis thickness was similar between the groups (p = 0.343); however, patients with knee osteoarthritis exhibited significantly smaller pennation angles (p < 0.001) and lower Gmean values (p = 0.009). Sex-stratified analysis revealed a reduced pennation angle in females (p = 0.003) and a smaller pennation angle (p = 0.036) and lower Gmean value (p = 0.013) in males with knee osteoarthritis. Conclusion Patients with knee osteoarthritis demonstrated significantly decreased gastrocnemius medialis pennation angles and Gmean values compared with those in controls, with sex-specific differences: males exhibited lower Gmean values, whereas females showed no difference. Gastrocnemius medialis ultrasonography may serve as an effective tool for detecting knee osteoarthritis-related biomechanical changes, supporting clinical assessment and rehabilitation planning.