Ultrasound-Guided Muscle Enhancement and Support Therapy (MEST): Protocol Standardization and a Pilot Study in Refractory Chronic Pain After Total Knee Arthroplasty.

PURPOSE: Muscle enhancement and support therapy (MEST) using bidirectional barbed polydioxanone filaments has been introduced for knee osteoarthritis, but the original technique relies on surface anatomical landmarks without imaging guidance. This study aimed to establish a standardized ultrasound-guided protocol for MEST targeting the vastus medialis obliquus (VMO) and report preliminary clinical outcomes in patients with refractory chronic knee pain following total knee arthroplasty (TKA). PATIENTS AND METHODS: This single-center retrospective pilot study included three patients (five treated knees) with chronic knee pain after TKA who underwent ultrasound-guided MEST between August 2025 and January 2026. The standardized protocol involved identifying the VMO midpoint in the short-axis view, rotating the probe to visualize muscle fibers to guide needle insertion, and using color Doppler to identify major vessels along the planned needle path. A needle was advanced in-plane along the VMO long axis to traverse the muscle belly while avoiding vascular structures for filament placement. Outcomes were assessed at baseline and at 4, 8, and 12 weeks using the Numeric Rating Scale (NRS), functional scores (walking and stair-climbing), ultrasonographic effusion grading, and patient-reported global effectiveness. RESULTS: The protocol was successfully executed in all five cases, allowing clear visualization of the VMO and filament placement spanning its full thickness. Four cases achieved a ≥50% reduction in NRS at 8 weeks. Walking and stair-climbing scores improved in most cases at 8 weeks and in all cases at 12 weeks. Complications were minimal, including mild ecchymosis and filament protrusion. No serious adverse events occurred. CONCLUSION: The standardized ultrasound-guided MEST protocol targeting the VMO appears technically feasible and safe. These preliminary findings suggest that MEST may be a potential treatment option for refractory chronic pain following TKA and warrant further prospective investigation.