Efficacy and safety of electroporation and MTX combination therapy for the patients with RA

INTERVENTION: * Evaluate the articular synovitis by gray and power dopplar scale using ultrasound (US). * Injection MTX (5mg/ml, 1ml) into MP or PIP joint using guide of US. After three minutes, perform electroporation for four angles with US gel. * Condition of electroporation is 50V/cm 250ms 4puluse. * Single intervention of injection MTX or combination of MTX and electroporation. Evaluation is performed at 2, 4, 12, and 26 weeks after baseline. * Evaluate the articular synovitis by gray and power dopplar scale using ultrasound (US). * Injection MTX (5mg/ml, 1ml) into MP or PIP joint using guide of US. * Single intervention of injection MTX or combination of MTX and electroporation. Evaluation is performed at 2, 4, 12, and 26 weeks after baseline. CONDITION: rheumatoid arthritis PRIMARY OUTCOME: Disease activity of local inflammation by Visual Analogue Scale (VAS) SECONDARY OUTCOME: 1. Ultrasound assessment: Gray and power dopplar scale of local site.; 2. Disease activity assessment: Mean value of DAS28, Mean change from baseline of DAS28.; 3. Joint destruction: Change of modified Total Sharp Score (mTSS) from baseline. INCLUSION CRITERIA: * Rheumatoid arthritis (RA) * No limitation of duration of RA * Patient who are recieving standard RA treatment * Patient who are stable disease activity during three months by Methotrexate * Patient who have swelling and tenderness at PIP or MP joint by positive power dopplar of ultrasound * Patient who are stable disease activity during three months by Steroid or biologic agent