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.
Knee osteoarthritis is one of the most common musculoskeletal disorders worldwide and is frequently associated with chronic pain, impaired mobility, and reduced quality of life. Genicular nerve block has become an established minimally invasive treatment for patients with persistent pain despite conservative management. However, substantial variability exists in treatment response, highlighting the need for reliable predictors of clinical success. Recent studies have suggested that ultrasound-derived muscle measurements may provide objective information regarding muscle quality and sarcopenia. The Sonographic Thigh Adjustment Ratio (STAR), defined as anterior quadriceps muscle thickness normalized to body mass index (BMI), has been proposed as an ultrasound-based indicator of muscle mass. Nevertheless, its potential role in predicting the response to interventional pain procedures has not been investigated. This prospective observational cohort study will enroll patients with symptomatic knee osteoarthritis who undergo ultrasound-guided genicular nerve block as part of routine clinical care. Before the procedure, ultrasound measurements of anterior quadriceps muscle thickness and subcutaneous fat thickness will be obtained. STAR will be calculated by dividing anterior quadriceps muscle thickness by BMI. Clinical outcomes will be assessed using validated pain and functional outcome measures during follow-up. The primary objective is to evaluate whether STAR predicts treatment response after genicular nerve block. Secondary objectives include investigating the predictive value of quadriceps muscle thickness and subcutaneous fat thickness individually and exploring their relationship with pain reduction and functional improvement.
Study Type
OBSERVATIONAL
Enrollment
30
Ultrasound-guided genicular nerve block was performed as part of routine clinical care in patients with symptomatic knee osteoarthritis. The superomedial, superolateral, and inferomedial genicular nerves were targeted using a standardized ultrasound-guided technique. A standardized injectate consisting of bupivacaine, dexamethasone, and normal saline was administered to each target nerve. The procedure was performed by an experienced pain physician using the same protocol for all participants.
University of Health Sciences Gaziosmanpaşa Physical Therapy and Rehabilitation Training and Research Hospital
Istanbul, Turkey (Türkiye)
RECRUITINGTreatment Response at 1 Month Following Genicular Nerve Block
Treatment response will be defined as a ≥50% reduction in Visual Analog Scale (VAS) pain score from baseline at 1 month after ultrasound-guided genicular nerve block. The predictive value of baseline Sonographic Thigh Adjustment Ratio (STAR) for 1-month treatment response will be evaluated.
Time frame: 1 month
Responder Pattern After Genicular Nerve Block
Participants will be classified according to pain response pattern after genicular nerve block: non-response, defined as less than 50% reduction in VAS pain score at 1 month; transient response, defined as at least 50% reduction at 1 month but less than 50% reduction at 3 months; and sustained response, defined as at least 50% reduction at both 1 and 3 months. The association between baseline STAR and responder pattern will be evaluated.
Time frame: 1 month, and 3 months
WOMAC Score
The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is a self-administered questionnaire used to evaluate knee and hip osteoarthritis. The global score ranges from 0 to 96, where 0 represents the best possible outcome (no pain or functional limitations) and 96 represents the worst possible outcome (severe pain and maximal functional limitations). Higher scores indicate a worse clinical outcome.
Time frame: Baseline, 1 month, and 3 months
Five Times Sit-to-Stand Test
Change in functional performance assessed using the Five Times Sit-to-Stand (5xSTS) test. The Five Times Sit-to-Stand (5xSTS) test assesses functional lower extremity strength and transitional movements. The outcome is recorded as the total time (in seconds) required for the participant to complete five consecutive sit-to-stand cycles as quickly as possible from a standard chair. The minimum possible time is 0 seconds, and a maximum cutoff score of 30 seconds is applied for participants who are unable to complete the task. Higher scores (longer times) indicate a worse outcome (poorer functional performance and lower extremity strength).
Time frame: Baseline, 1 month, and 3 months
Change in Pain Intensity
Change in Visual Analog Scale (VAS) pain score from baseline after ultrasound-guided genicular nerve block. Pain intensity is assessed using the Visual Analog Scale (VAS). The scale consists of a horizontal line where the minimum value is 0 (representing "no pain") and the maximum value is 10 (representing "the worst possible pain"). Participants mark their current pain level on this line. Higher scores indicate a worse outcome (greater pain intensity).
Time frame: Baseline, 1 month, and 3 months
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