Sonographic Thigh Adjustment Ratio and Subcutaneous Fat Thickness as Predictors of Genicular Nerve Block Response in Knee Osteoarthritis

Knee osteoarthritis (KOA) is a leading cause of chronic pain and disability. Although genicular nerve block (GNB) is an effective treatment for many patients, treatment response varies considerably. Identifying imaging biomarkers that predict clinical response may improve patient selection and optimize treatment outcomes. This prospective observational study aims to evaluate whether the Sonographic Thigh Adjustment Ratio (STAR), calculated as anterior quadriceps muscle thickness divided by body mass index (BMI), and subcutaneous fat thickness are associated with pain relief following genicular nerve block in patients with symptomatic knee osteoarthritis. Ultrasound measurements will be obtained before the procedure, and clinical outcomes will be assessed during follow-up. The primary objective is to determine whether sonographic muscle parameters can predict treatment response after GNB.

Inclusion Criteria: * Age ≥45 years. * Symptomatic bilateral knee osteoarthritis with Kellgren-Lawrence grade 3 or 4. * Visual Analog Scale (VAS) pain score ≥4 at rest or during movement. * Scheduled to undergo first ultrasound-guided genicular nerve block. * No intra-articular knee injection within the previous 3 months. * Considered unsuitable for or awaiting total knee arthroplasty. * Ability to provide written informed consent. Exclusion Criteria: * Inflammatory arthritis, rheumatoid arthritis, or crystal arthropathy. * Previous knee surgery or knee prosthesis. * Active local or systemic infection. * Anticoagulant therapy or bleeding disorders. * Contraindication to corticosteroids (including uncontrolled diabetes mellitus). * Allergy to study medications. * Neurological disorders causing neuropathic knee pain. * Dementia or inability to complete study assessments. * Additional interventional procedures or surgery during follow-up.