The purpose of this study is to determine whether bipolar intraarticular pulsed radiofrequency method has a superiority to unipolar mode in the treatment of chronic knee pain.

After obtaining written informed consent and ethics committee approval, 100 patients aged 20-70 years with osteoarthritis having knee pain over 3 months are recruited to the randomized, double-blind study. Exclusion criteria are a chronic knee pain caused by infection, inflammation, tumors, and fractures or a history of acute knee pain, previous knee surgery, connective tissue diseases, neurologic or psychiatric disorders, administration of steroids or hyaluronic acids within the last three months, coagulation disorders and local infection at the site of intervention planned.

Patients are admitted to the preoperative unit 15 minutes before the procedure. After intravenous access is established by a 20 gauge cannula, all patients are monitored with non-invasive blood pressure (NIBP), electrocardiogram (ECG) and peripheral oxygen saturation (SpO2) (Drager-Primus Anesthesia Device Monitor, Drager Medical Systems, Inc 16 Electronics Avenue, Denver, MA 01923 USA) in the operating room before the beginning of procedure. Patients are randomly allocated into two groups in a 1:1 ratio by a computer-generated list. Allocation is provided with sealed envelopes containing group named paper.

After patients are positioned to supine, a pillow is placed to support below their knee to be treated. Anteroposterior (AP) fluoroscopic image of the knee joint is obtained with C-arm fluoroscopy. 1% of lidocaine is injected 2 ml under the skin at locations corresponding to joint space both of sides of the patellar ligament and A 10 cm 22-gauge two radiofrequency electrode needles with a 5 mm active tip (NeuroTherm® RF Cannula) are bilaterally inserted at the same points and advanced under fluoroscopic guidance entering the cavity of the knee joint at the both medial and lateral sites until needle tips are in the middle of the joint space. Pulsed Radiofrequency (PRF) is bilaterally performed in 42oC of temperature during ten minutes. After positioned to supine, a pillow is placed to support below their knee at the planned procedure site. Anteroposterior (AP) fluoroscopic image of the knee joint is obtained with C-arm fluoroscopy. Under fluoroscopy at locations corresponding to joint space both of sides of the patellar ligament, 1% of lidocaine is injected 2 ml under the skin and at the same points with 22 gauge of thickness, 10 cm in length, 5 mm of length active tipped two radiofrequency electrode needles (NeuroTherm® RF Cannula) are bilaterally inserted and advanced under fluoroscopy entering the cavity of the knee joint at the both medial and lateral sites until needle tips are in the middle of the joint space. PRF is bilaterally performed with a unipolar mode, 45V voltage, 2 Hz frequency, at a temperature of 42oC, 10 msec pulse width for 10 minutes in group U. The same procedure is bilaterally performed with a bipolar mode for 10 minutes in group B. All procedures are performed by one practitioner who is not informed about the type of procedure (unipolar or bipolar mode) and also patients are not aware of which type of treatment received.

If any complication is not observed for one hour after the procedure, the patients are discharged. Paracetamol is prescribed for the supplemental analgesic requirement.

The degree of pain is assessed with a 10-cm VAS. "0" identifies the least possible pain and "10" determines the most severe pain that can be considered. We evaluate the health status of patients by the WOMAC index which is valid and reliable self-administered questionnaire including 24 items divided into 3 subscales (pain, stiffness, and physical function).(1,2) Visual Analog Scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index LK 3.1 (WOMAC) and supplemental analgesic requirements, any side effects and complications such as a motor or sensorial loss are recorded in both groups at before the procedure and at 1, 4, and 12 weeks after the procedure. We assess the patients when they are requested to our clinic for clinical examination. We also call them by telephone to any further advice.

The primary outcomes are VAS scores measuring knee pain at 1, 4, and 12 weeks after the procedure. Secondary outcomes are WOMAC scores to evaluate the quality of life and the functional response of treatment of patients and the incidence of adverse effects.

Inclusion Criteria:

• Patients aged 20-70 years
• Patients with osteoarthritis having knee pain over 3 months

Exclusion Criteria:

• Chronic knee pain caused by infection, inflammation, tumors, and fractures
• A history of acute knee pain, previous knee surgery, connective tissue diseases, neurologic or psychiatric disorders,
• The administration of steroids or hyaluronic acids within the last three months
• Coagulation disorders
• Local infection at the site of intervention planned