Correlation between knee pain and quadriceps condition in osteoarthritis rats treated with cog polydioxanone filaments.

Background: Weakness in the quadriceps muscle significantly contributes to the development and progression of knee osteoarthritis (OA), characterized by pain and impaired function. This study aimed to assess structural and functional recovery in the quadriceps and its association with knee OA pain following treatment with the Muscle Enhancement and Support Therapy (MEST) device. MEST involves inserting cog polydioxanone filaments directly into muscle tissue to help alleviate OA pain. Methods: Knee OA was induced in Sprague-Dawley rats using monoiodoacetate injections, followed by MEST or a sham treatment. Five weeks post-MEST treatment, quadriceps recovery was evaluated by measuring entire muscle volume, hindlimb torque, tissue morphology, and key structural and functional biomarkers. Pain was assessed through paw withdrawal thresholds and weight-bearing distribution. Correlations between muscle measurements and pain levels were then analyzed. Results: MEST treatment resulted in significant increases in quadriceps volume, enhanced hindlimb torque, and elevated expression of α-actin, myosin, and the mitochondrial marker cytochrome c oxidase subunit 4, along with reductions in OA pain. These enhancements in muscle condition were closely associated with pain relief in OA. Conclusions: This study shows that MEST improves the quadriceps condition, including muscle volume, structure, function, and energy metabolism, and relieves knee OA pain, which are closely linked. These findings may suggest that promoting quadriceps recovery through MEST could be a promising approach for managing OA-related pain.