This is a prospective, randomised, interventional, double blinded study to compare the clinical outcomes of thermal vs. pulsed radiofrequency (RF) treatment of the genicular nerves in patients with painful osteoarthritis (OA) of the knee.

Population: 60 patients, aged 50 and above, with painful OA of the knee. Interventional measures: Pulsed or heated RF treatment of the genicular nerves of the involved knee.

Outcome measures: primary - fraction of patients experiencing improvement of 50% or higher in their average pain rating during stair climbing.

secondary - improved quality of life

• improved functional capacity
• comparison of side effects and adverse events
• change in the consumption of analgesic medications

Pre-intervention assessment Pain intensity during stairs climbing using VAS 1-100 numerical rating scale. Analgesics consumption. Quality of life using WOMAC questionaires. A physician will further examine them and will enroll them signing an informed concent.

A diagnostic block with lidocaine 2% (2ml for each nerve - total volume of 6ml per knee) of 3 genicular nerves (upper medial and lateral and lower medial branches) will be performed, guided either by ultrasound or by fluoroscopy.

Participants will be asked to fill in a VAS questionnaire shortly (up to one hour) after undergoing the diagnostic blocks.

Participants achieving a relief of >50% in pain intensity during stairs climbing will be considered to have responded to the diagnostic block and will be randomized.

Randomization

Recruited participants will be randomized into two groups:

1. Heated RF ablation
2. Pulsed RF ablation

Blinding Both the patient and the assessing physician will be blinded to the group to which the patient has been allocated. The physicians performing the treatment will be blinded as well.

Intervention

Heated RF ablation of the genicular nerves will be performed as follows:

1. In the supine position, aseptic preparation of the skin and sterile coverage of the procedure area will take place.
2. After the administration of local anesthesia to the skin with lidocain 2% (1-1.5cc for each injection site, fluoroscopy guided placement of three 22 gauge 50mm or 100mm straight RF cannulas in the proximity of 3 of the genicular nerves: 2 on both sides of the distal femoral shaft-epiphysis border and one on the medial proximal tibial epiphyseal-shaft border.
3. Sensory stimulation at 50 Hertz will be used to test the proper position of the needle, expected to generate paresthesia in the distribution of the affected nerve, at a voltage in the range of 0.3-0.8 Volts. Motor stimulation at 2 Hz will be used to exclude proximity of the cannula to motor nerves.
4. 1 ml of 2% lidocaine will be injected into each cannula.
5. 180 sec 80 degrees heated RF ablation of the nerves will be performed. Needles will be left in place for additional 420 seconds to match the treatment duration of the pulsed RF group.
6. Injection of a total amount of 80 mg methylprednisolone and lidocaine 2% 2cc to the 3 intervention sites.

Pulsed RF ablation of the genicular nerves will be performed similarly to the heated RF ablation with the only difference being that the treatment will include a 600 sec of 42 degrees heating of the three-genicular nerves.

Blinding Both the patient the assessing and performing physicians will be blinded to the group to which the patient has been allocated.

Post-procedural assessment Participants will be assessed 3 days and 30 days after the procedure (phone questionnaires) and a clinical follow-up visits in 3 and 6 months after the procedure.

The assessment will include:

1. Two telephone interviews, in which the patient will report the average severity of pain on a 1 to 100 numerical rating scale and will fill up a WOMAC questionnaire regarding the treated knee in the prior 24 hours.
2. Two clinic follow-up visit, during which the patients will fill-in a questionnaire of pain intensity after stairs climbing using VAS 1-100 numerical rating, analgesic consumption, quality of life measures using the WOMAC questionaire. Questionnaires filling-in will be aided and supervised by research assistants blinded to the intervention the participants have received.

Inclusion Criteria:

• Radiologically proven OA of knee with a 2. Kellgren-Lawrence scale (K-L score) of 3 to 4.
• Clinically proven OA of knee with an Oxford knee score of 0 to 30 (representing moderate to severe OA).
• Chronic knee pain due to the OA of knee (>3 months) of at least moderate severity by a Visual Analogue Scale (VAS) 4 and above.
• Signed informed consent

Exclusion Criteria:

• Acute knee pain
• Disease that preclude per clinician decision interventional treatment.
• Allergic reaction to the injected substances (triamcinolone, lidocaine)
• Injections to the knee during the 3 months preceding recruitment
• Distorted knee intervention due to any cause, which interferes with the radiological identification of targeted RF sites.
• Anticoagulation treatment that cannot be stopped.