1) Goals: Our goal in this study is to evaluate the effect of intra-articular radiofrequency use on patients' relief of pain and their degree of change in knee movement. 2) Design: After diagnosing knee osteoarthritis in patients, and ruling out other disorders such as rheumatoid arthritis and hemophilia and opioid or alcohol addiction, the patients will be enrolled in this study. We do not have any age limit for this procedure. We will explain to the patients about the advantages and disadvantages of this intervention which is intra-articular RF and written informed consent is achieved. Then before performing the procedure, the patient's pain with visual analogue score (VAS) and the knee joint ROM would be evaluated and recorded in the questionnaire. After performing the procedure, the patient's pain with VAS and the ROM of the joint plus the amount of used analgesic (400 mg Gelofen if VAS>3) will be assessed again after 1, 4, 8, and 12 weeks. 3) Method: Then the patient would be admitted to the pain OR and under sterile condition after prep-drape on supine position, the RF needle (50 mm) would be inserted under fluoroscopy into the joint and pulsed RF for 15 minutes and 42 degrees will be applied. After being transported to the PACU, the patients would be monitored for one hour regarding complications. 4) The inclusion criteria consist of patients diagnosed as having Knee osteoarthritis; and the other causes of knee pain have been ruled out; The exclusion criteria includes addiction to opium or alcohol ; other rheumatologic disorders ;rheumatoid arthritis; hemophilia 5) Interventions: After performing the intra-articular radiofrequency procedure, the patient's pain with VAS and the ROM of the joint plus the amount of used analgesic( 400 mg Gelofen if VAS>3) will be assessed again after 1 , 4, 8, and 12 weeks. 6) Main outcome variables: The pain score (VAS); the joint's ROM; and the amount of analgesic use by the patients are our main outcome variables.