Effect of Saphenous Nerve and Nerve to Vastus Medialis Block Within Subsartorial Femoral Triangle on Quadriceps Strength

Inclusion Criteria: * Eligible patients are all ASA class I-III, age 18-80 years, and have plan to perform SSFTB at Thammasat University Hospital consecutively Exclusion Criteria: * Exclusion criteria are patients who refuse to participate the study, morbid obesity (BMI ≥ 35 kg.m2), lower extremity neurological dysfunction, performing other peripheral nerve blocks, patients who cannot cooperate or measure MVIC, difference of quadriceps strength between two side of knees more than 10 percent, and SSFTB is not finally performed or failed block.