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Knee osteoarthritis (KOA) is a chronic degenerative osteoarthropathy that occurs mostly in the middle-aged and elderly population, and is currently thought to be caused by the difficulty of chondrocytes to maintain the extracellular matrix, as well as the dynamic imbalance between subchondral bone synthesis and degradation[1]. The current recommended treatments for KOA are mainly conservative, including non-pharmacologic treatments and pharmacologic treatments . Pain symptoms are present throughout the course of KOA, and most patients gradually evolve from intermittent, active pain to chronic, persistent pain, with a corresponding increase in the degree of physical impairment. In addition, for many patients with severe pain, total knee arthroplasty (TKA) or other surgical treatments are used. Unfortunately, there are still some patients who undergo surgery who have poor postoperative outcomes or are left with chronic pain. Therefore, pain management has a crucial role in the treatment of KOA by controlling knee pain, improving joint function, slowing down disease progression, and thus enhancing patients' quality of life[2].

Radiofrequency (RF) therapy, as a physical minimally invasive therapy, is widely used in the treatment of trigeminal neuralgia, radicular cervical spondylosis, postherpetic neuralgia, and other diseases because of its subtle action and high safety. Choi et al. introduced this technique for the treatment of chronic pain caused by KOA by targeting the peripheral nerve of the knee using radiofrequency ablation (RFA) technology under ultrasound guidance. The study showed significant improvement in knee pain and function in all treated patients without any adverse events[3]. In the subsequent years of exploration, the radio-frequency devices were gradually updated and improved, and the methods were more diverse. Pulsed radiofrequency (PRF), as a safer and less invasive analgesic technique, always maintained at a safe temperature (≤42℃) that does not damage living tissues, and with less nerve and peripheral tissue destructive compared with the traditional RFA. It may provide substantial clinical and functional benefits to patients with chronic knee pain after KOA or TKA[4].

PRF has been demonstrated to have real biological effects in cell morphology, synaptic transmission and pain signaling tam. At present, the research on the mechanism of pain relief by PRF is mainly reflected in the following two aspects. Relevant electrophysiological experiments have shown that PRF can selectively block neural activity in C fibers. PRF acts at a mild temperature, not reaching the threshold of 45°C for neuronal tissue destruction, so that the damage to the nervous system while producing analgesia is usually reversible. On the other hand, the treatment can exert immune system regulation effects, reduce local serum TNF-alpha, IL-6 and other related inflammatory cytokine levels, inhibit the occurrence of chronic inflammatory response, and relieve long-term chronic pain[5]. At the same time, it can impede articular cartilage damage and apoptosis, delaying disease progression. In addition, the exploration of the mechanism of action of PRF is not limited to the above mechanisms. Some researchers have suggested that it may involve affecting central nervous system plasticity, such as promoting the transcription of endogenous opioid precursor mRNA, inhibiting microglia activity in the posterior horn of the spinal cord, and interfering with the downstream pain inhibitory pathway[6].

Reference

  1. Kılıçkesmez Ö, Dablan A, Güzelbey T, Cingöz M, Mutlu İN. Comparative Analysis of Transpedal and Transfemoral Access During Genicular Artery Embolization for Knee Osteoarthritis. Cardiovasc Intervent Radiol. 2024 May 24. doi: 10.1007/s00270-024-03757-2. Epub ahead of print.

  2. Henriksen M, Runhaar J, Turkiewicz A, Englund M. Exercise for knee osteoarthritis pain: Association or causation? Osteoarthritis Cartilage. 2024 Jun;32(6):643-648.

  3. Choi WJ, Hwang SJ, Song JG, Leem JG, Kang YU, Park PH, Shin JW. Radiofrequency treatment relieves chronic knee osteoarthritis pain: a double-blind randomized controlled trial. Pain. 2011 Mar;152(3):481-487.

  4. Klem NR, Smith A, O'Sullivan P, Dowsey MM, Schütze R, Kent P, Choong PF, Bunzli S. What influences patient satisfaction after total knee replacement? A qualitative long-term follow-up study. BMJ Open. 2021 Nov 22;11(11):e050385.

  5. Mantyh PW. Mechanisms that drive bone pain across the lifespan. Br J Clin Pharmacol. 2019 Jun;85(6):1103-1113.

  6. Sam J, Catapano M, Sahni S, Ma F, Abd-Elsayed A, Visnjevac O. Pulsed Radiofrequency in Interventional Pain Management: Cellular and Molecular Mechanisms of Action - An Update and Review. Pain Physician. 2021 Dec;24(8):525-532.