Pulsed Radiofrequency and Osteoarthritic Chronic Knee Pain

The purpose of this study is to investigate the efficacy and safety of pulsed radiofrequency of the saphenous nerve in the treatment of pain due to knee osteoarthritis (OA). The investigators will conduct real pulsed radiofrequency or sham, over the saphenous nerve during 4 separate sessions. The investigators will evaluate pain intensity, quality of life, function, and disability via clinical validated scales. The research question is whether pulsed radiofrequency can lessen knee pain and improve function and quality of life in patients with chronic knee pain due OA. It is hypothesized, that less knee pain and improved function, and quality of life after the pulsed radiofrequency sessions.

Osteoarthritis (OA) affects 10% of the population over 60 years of age each year, with an increasing incidence related to population aging. This disease costs 1-2.5% of GDP on average in Europe when combining direct and indirect costs: it is therefore the 9th leading cause of disability adjusted life years. The knee is the most commonly affected joint, for which there is no treatment able to stop joint degeneration as of today: common treatment regimens include pharmacological therapy, joint infiltrations, neuromodulation techniques, and total knee arthroplasty when indicated. However, each patient responds differently and therefore necessitates a tailored approach. Pulsed radiofrequency (PRF), a neuromodulating technique that potentiates the descending analgesic pathway by avoiding Wallerian degeneration, has as of today been targeted intraarticularly or to the genicular nerves, yielding unreliable results in both cases, perhaps due to small samples, lack of long term follow ups, and absence of control groups. The goal of this study is to explore the efficacy and safety of PRF on the saphenous nerve, an exclusively sensory nerve that is responsible for pain perception on the medial surface of the lower limb, often associable with OA. In particularly, the investigators will evaluate the effect of PRF on pain reduction, function, disability, and quality of life in patients with knee OA. This study will include 20 participants suffering from knee OA, and the participants will enroll if infiltrating their saphenous nerve with 2mL of 2% lidocaine reduces their Numeric Pain Rating Scale (NRS) pain perception by at least 60%. The participants will be allocated consecutively to randomization as an intervention order using the tool from the randomization.com website (Dallal GE, http://www.randomization.com). The investigators will use the second generation suggested for crossover studies. The participants will be randomized into a PRF sham control group or a real PRF group and the investigators will follow up at 2 weeks (T1), 1 month (T2), 3 months (T3), and 6 months (T4) by acquiring their NRS, Oxford Knee Score, and SF-36 questionnaire. After 6 months, the participants will be crossed-over and the follow-up method will be repeated.

The participant will receive real pulsed radiofrequency for 2 minutes at a frequency of 2 pulses per second (2Hz) while lie in the supine position with their leg of interest partially flexed about 45 degrees and externally rotated. The full procedure will take eight minutes, composed of four sessions of 2 minutes in which the temperature was maintained below 42°C.

Identical to the real pulsed radiofrequency, except the participants will only receive the initial 2 seconds of ramp-up, after which the device will switch-off for the rest of the session and will turn-on again at the end of the session.

Pulsed radiofrequency is a novel therapeutic modality with many potential applications in pain management.

Changes in Pain severity will be measured by Numeric Pain Rating Scale (score from 0 to 10, where 0 is described as "no pain" and 10 as "worst pain imaginable").

Changes in quality of life will be measured by SF-36. The Italian version of SF-36 will used to understand the health related quality-of -life of the participants over the past four weeks. The eight health concepts: limitations in physical activities because of health problems; limitations in social activities because of physical or emotional problems; limitations in usual role activities because of physical health problems; bodily pain; general mental health (psychological distress and well-being); limitations in usual role activities because of emotional problems; vitality (energy and fatigue); and general health perceptions will be searched. These outcomes will be grouped as physical component summary and mental component summary. The norm data is 0-100, the health related quality of life is increases as the scores are increased. The average score is 50.

Changes in in knee function and pain will be measured by Oxford Knee Score. The Oxford Knee Score questionnaire consists of 12 questions that cover function and pain of the knee. Each question is scored from 0 to 4 (0 being the worst outcome and 4 being the best). The overall score is the sum of all items and can range from 0 to 48, with higher scores corresponding to better outcomes.

Inclusion Criteria: Chronic knee pain (present for at least 6 months), of moderate-severe intensity (assessed by NRS => 6), not responsive to conservative treatments (physiotherapy, oral analgesics). Diagnosis of knee osteoarthritis confirmed by instrumental investigation (X-ray and/or MRI) and Oxford Knee Score = <35. Positivity to the diagnostic block of no. saphenous (defined as a reduction of at least 50% of the NRS score). If the patient is taking opioids or other morphine equivalents, the dosage should not be changed within 3 months prior to the study enrollment visit. Exclusion Criteria: Body Mass index > 40 kg /m2 History of systemic inflammatory disease, uncontrolled diabetes mellitus, neoplastic pathology, coagulopathy Previous knee replacement implant

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