Learning objectives.
By reading this article, you should be able to:
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Describe the innervation of the knee joint and outline neural targets for radiofrequency ablation (RFA) for relieving pain from osteoarthritis of the knee joint.
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Illustrate anatomical targets under fluoroscopy and ultrasound guidance.
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Discuss the various available RFA modalities for denervating the knee joint.
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List the factors associated with better outcomes of RFA for denervating the knee joint.
Key points.
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Osteoarthritis (OA) of the knee is widely prevalent and pain is its most common presenting symptom.
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Radiofrequency ablation (RFA) of the innervation to the knee joint is a minimally invasive option that should be offered if first-line treatments for OA of the knee (physiotherapy, analgesics and intra-articular injections) are ineffective and joint arthroplasty is not a preferred option.
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Innervation of the knee joint is complex with contributions from branches of three major nerves: femoral, sciatic and obturator.
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Accurate identification and RFA of the articular neural branches to the knee joint can improve pain-related outcomes.
Osteoarthritis of the knee joint, a condition prevalent in older individuals, is caused by gradual wear and tear and progressive erosion of the articular cartilage. As life expectancy and the prevalence of obesity continue to increase, the prevalence of knee osteoarthritis is expected to grow. Around 30% of >45-yr-olds exhibit radiographic signs of knee osteoarthritis, with approximately half of them reporting the triad of pain, stiffness and difficulty with walking.1,2 Although physiotherapy, medications and injections of steroids and viscosupplements can ameliorate pain for some patients with arthritis of the knee, many individuals continue to report moderate-to-severe pain. Radiofrequency ablation (RFA) of the innervation to the knee has emerged as a viable option for analgesia in patients who fail standard conservative measures and are not suitable for joint replacement. Although the first randomised controlled trial to evaluate RFA of innervation to the knee was published only in 2011, several studies of clinical outcomes have been published since then.3 This has coincided with a number of anatomical studies focused on knee joint innervation.
This review discusses the relevant anatomy of nerves targeted, published clinical data on variations of RFA of the knee, and factors affecting outcomes.
Innervation of the knee joint
Roberts and colleagues published a comprehensive review in 2020 of the evidence demonstrating that the knee joint is innervated by the terminal branches of the femoral and obturator nerves, and articular branches of the sciatic nerve.4 Most research on denervating the knee joint has focused on the innervation of the anterior knee joint because of the proximity of the sciatic nerve, popliteal artery and vein to the posterior aspect of the knee.
Anterior knee
Based on cadaveric dissection studies, the innervation of the anterior knee joint can be divided into four quadrants.4, 5, 6, 7 The three nerves responsible for innervating the superomedial quadrant of the knee joint are as follows, listed in anterior to posterior order:
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the nerve to vastus medialis (NVM),
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the medial branch of the nerve to vastus intermedius (NVI),
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the superior medial genicular nerve (SMGN).5
The superolateral quadrant receives innervation from four nerves, from anterior to posterior:
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the nerve to vastus lateralis (NVL),
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the lateral branch of the nerve to NVI,
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the articular branch of the common fibular nerve,
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the superior lateral genicular nerve (SLGN).5
The inferomedial quadrant is innervated by two nerves:
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the infrapatellar branch of the saphenous nerve (IPBSN) (superiorly) and the inferior medial genicular nerve (IMGN) (inferiorly),
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the inferolateral quadrant is innervated by two nerves, arranged in a superior to inferior order: the inferior lateral genicular nerve (ILGN) and the recurrent fibular nerve.5
However, the inferior lateral quadrant of the knee is often not targeted by RFA techniques because of the proximity of the common peroneal nerve to the sensory articular branches of the knee.
Posterior knee
Most studies have reported that the innervation of the posterior aspect of the knee joint is primarily from the popliteal plexus, which comprises the articular branch(es) of the tibial nerve innervating the entire capsule of the posterior knee joint and the posterior branch of the obturator nerve providing innervation to the superomedial portion of the capsule.6,8, 9, 10, 11 In addition, the posterior knee joint is also innervated by either the posterior branch of the common fibular nerve or the sciatic nerve innervating the superolateral aspect of the posterior knee.11
RFA techniques and neural targets for ablation
Neural targets
The use of genicular RFA as a treatment option for chronic knee osteoarthritis started after the publication of a randomised controlled study that compared it with sham lesioning, and identified the SMGN, SLGN and IMGN as primary targets for denervation.3 However, there were concerns about the anatomical basis of neural targets and the reproducibility of these results in clinical practice.5,12 Recent investigations have focused on the complex innervation of the knee joint, suggesting the need to re-evaluate the neural targets and their imaging correlates with the goal of improving the efficacy of genicular RFA.12 The concept of selective denervation (i.e. selectively targeting the articular branches based on pain location) has been proposed recently. For instance, to address superomedial knee pain we target the SMGN, the medial branch of NVI, and the NVM (Table 1).5
Table 1.
Summary of classical and revised neural targets for knee denervation. AP, anteroposterior.
| Neural target | Innervation territory | Fluoroscopy target (classical) | Fluoroscopy target (revised) | Ultrasound target |
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| Superomedial genicular nerve (SMGN) | Superomedial quadrant of the anterior knee capsule |
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| Superolateral genicular nerve (SLGN) | Superolateral quadrant of the anterior knee capsule |
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| Infrapatellar branch of the saphenous nerve (IPBSN) | Inferomedial quadrant of the anterior knee capsule |
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| Inferomedial genicular nerve (IMGN) | Inferomedial quadrant of the anterior knee capsule |
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| Recurrent fibular nerve | Inferolateral quadrant of the anterior knee capsule |
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Image guidance
Both fluoroscopy and ultrasound can be used to perform blocks of genicular nerves (for prognosticating response to RFA or for therapeutic pain relief) and to position the RFA probe precisely near the targeted nerves. An RCT comparing ultrasound with fluoroscopy-guided genicular nerve block showed that both imaging approaches had comparable outcomes in terms of pain relief, safety and functional improvement.13 Similar results have been reported for genicular RFA.14 However, another recent RCT comparing the two imaging modalities showed that patients assigned to ultrasound-guided RFA of the knee had better outcomes in both Visual Analogue Scale (VAS) score and Western Ontario and McMaster Universities Arthritis Index (WOMAC) score at 1-month and 3-month follow-ups compared with participants who received fluoroscopy-guided RFA.15 It may not be vital to choose one imaging modality over another, with some physicians using both modalities to perform genicular RFA.16
Role of diagnostic or prognostic nerve blocks
The reliability of diagnostic genicular nerve block before RFA of the knee joint in predicting outcomes is doubtful. A randomised controlled study reported there was no significant difference in success rates (success defined as ≥50% reduction in pain at 6 months after RFA) between patients who underwent RFA without a prognostic block (64% successful) and those who received RFA only after a positive block (59% successful).17 More research is needed to define the role of diagnostic or prognostic genicular nerve blocks before proceeding with RFA.
Type of radiofrequency procedure
A variety of RFA techniques have been used, such as conventional (monopolar or bipolar) and cooled RFA, with all techniques associated with meaningful analgesia.18,19
The size of the lesion produced depends on the type and the size of the active tip. For conventional monopolar RFA, the commonly used 10 mm/18G active tip provides a larger lesion than the smaller 10 mm/22G active tip. This is because monopolar RFA produces a prolate spherical lesion around the active tip. Some modifications to the tip, such as those with protruded probes, modify the shape at the tip, so the lesion extends distally. In contrast, cooled RFA lesions are mostly produced with a 4 mm/17G active tip. Lesions produced by cooled RFA are more symmetrical (i.e. quasi-spherical) because of the thermodynamic effect of the cooling and unlike monopolar RFA, cooled RFA lesions project out of the tip. Larger sizes are generally expected with a longer active tip, but larger lesion sizes may not be better because of anatomical constraints. Vallejo and colleagues recently demonstrated that there is no significant clinical difference when using either cooled RFA (4 mm/17G active tip, 150 s) or monopolar RFA (10 mm/16G active tip, 90 s).20
With conventional RFA, McCormick and colleagues recommend RFA temperature >80°C for at least 90 s.21 However, with cooled RFA, larger lesions can be created because of circulating water within the probe that prevents tissue charring and desiccation.22 Variables for cooled RFA include a temperature of 60°C and a lesion time of 150 s to create an intralesional temperature of at least 80°C.21
The number of lesions and the type of RFA cannula can also affect the efficacy of lesioning. Because of the extensive innervation of the knee joint, Tran and colleagues suggested creating multiple lesions or using a multi-tined cannula to achieve larger lesions, in order to target all the desired articular branches effectively.5
Neural targeting with fluoroscopic guidance
The classical radiographic landmark for genicular nerves ablation as outlined by Choi and colleagues is located at the confluence of the femoral shaft and bilateral epicondyles for the SMGN and SLGN and the tibial shaft and medial epicondyle for the IMGN.3 On the lateral fluoroscopy view, the target is the midpoint of the femoral shaft for SMGN and SLGN, and the midpoint of the tibial shaft for IMGN RFA (Fig. 1). More recently, Fonkoue and colleagues proposed revised landmarks for fluoroscopic-guided knee denervation (Fig. 2).12,23 For theSMGN, the target is located just anterior to the adductor tubercle (AT) of the femur to capture the trunk of the SMGN before its bifurcation into its terminal branches. On the lateral view, the needle tip should be advanced posteriorly just in front of the AT. For the SLGN, the needle target on the A-P view is the upper edge of the lateral condyle. On the lateral view, the target is the junction between the superior edge of the lateral condyle and the posterior femoral cortex. The authors also suggested creating a series of three adjacent lesions given the variability of the course of the SLGN, with the potential for this modification to capture the two terminal branches of the SLGN (ascending [transverse] and descending branches), whereas the classic landmark would only capture the transverse branch. They also suggested adding the recurrent fibular nerve and the IPBSN as neural targets for RFA. Articular branches of the recurrent fibular nerve are usually avoided because of proximity to the common peroneal nerve. However, recent studies showed these branches can be targeted safely 1 cm below Gerdy's tubercle on the tibia.12,24 Fonkoue and colleagues suggested inserting the needle just distal to Gerdy's tubercle and advancing distally to reach bone 1 cm caudal to the inferior edge of the tubercle. For RFA of the IPBSN, the target is along a longitudinal line that is 4 cm medial to the apex of the patella and tibial tubercle (Fig. 3).7 The IPBSN is a particularly important target in patients with persistent neuropathic pain after total knee arthroplasty (TKA).25
Fig 1.
Fluoroscopy image illustrating classic fluoroscopy-guided targets (blue dots) in both anteroposterior (left) and lateral views (right) according to Choi and colleagues.3 LE, lateral epicondyle; ME, medial epicondyle.
Fig 2.
Fluoroscopy image illustrating revised targets (blue circles) according to Fonkoue and colleagues.23 (A) Target for superomedial genicular nerve (SMGN) just anterior to adductor tubercle. (B) Target for superolateral genicular nerve (SLGN) at the junction between the upper edge of the lateral epicondyle and posterior femoral cortex. (C) Anteroposterior view of revised targets for both SMGN and SLGN. Adding two more lesions, one above and one below the circle in the middle, may increase the chances of nerve capture.
Fig 3.
Treatment line (Hu line) for the infrapatellar branch of the saphenous nerve (IPBSN).
In a cadaveric study comparing classical and revised techniques for fluoroscopic-guided genicular nerves RFA, the accuracy rate for capturing the SMGN and SLGN was higher with revised targets (100% for the SMGN and 64% for the SLGN) compared with classical targets (0% for the SMGN and 35% for the SLGN).3,23 The accuracy rate for the IMGN was consistent at 100% for both techniques. Moreover, the revised targets were 100% accurate for capturing the IPBSN and recurrent fibular nerve, both not targeted by the classic targets.23 Given the variability in the bony contact of the SLGN, the authors suggested two or three contiguous lesions instead of only one lesion to capture both descending and transverse branches. They suggest one lesion at the junction of the lateral condyle and posterior cortex of the femoral shaft and two other lesions extending in a backward and distal direction, reaching the posterior edge of the lateral condyle. A recent retrospective study by Forero and colleagues demonstrated better pain and functional outcomes for up to 6 months by performing ablation targeting six nerves including the three genicular nerves, medial and lateral branches to the NVI and the recurrent fibular nerve to the genicular nerves.26
Neural targeting with ultrasound guidance
Ultrasound is radiation-free, and it allows visualisation of surrounding vessels. The classic ultrasound-guided technique relies on targeting the genicular nerves near the genicular arteries, which are located near the periosteum at the metaphyseal–diaphyseal junction.27 First, the probe is placed in a longitudinal plane on the lateral femoral or tibial shaft. Then, the probe is moved distally to visualise the femoral or tibial metaphyseal–diaphyseal junction, with the genicular artery located near the periosteum. (Fig. 4). The probe (skin)-to-junction depth is measured as the probe is rotated to a transverse orientation. The RF cannula is then inserted in-plane from anterior to posterior to reach genicular nerves near the periosteum.
Fig 4.
Ultrasound images of targets for superomedial genicular nerve in (A) long axis and (B) short axis, and inferomedial genicular nerve in (C) long axis and (D) short axis. (Figure reproduced with permission from Philip Peng Educational Series.)
Fonkoue and colleagues provided revised sonoanatomical targets that are different from that of the classic described technique.28 For the SMGN, scanning starts in a coronal plane at the level of the medial femorotibial joint, then the probe is translated upward and backward to visualise the AT, after which the probe is rotated to a transverse orientation and moved more posteriorly to visualise the posterior femoral cortex. The target is the junction between the superior medial condyle and the posterior femoral cortex. For SLGN, the probe is moved from the lateral femorotibial joint line superiorly to visualise the junction between the femoral shaft and lateral femoral condyle. Then the probe is rotated to a transverse orientation and moved posteriorly to identify the posterior part of the lateral condyle. The target is the junction between the superior lateral condyle and the posterior femoral cortex. For the IMGN, the authors described a technique like the classic technique targeting the nerve at the metaphyseal–diaphyseal junction near the genicular artery and underneath the medial collateral ligament.
Clinical evidence of efficacy of genicular RFA
Several studies have been published since the first RCT by Choi and colleagues supporting the use of radiofrequency denervation for knee joint.3 A systematic review found that RFA of innervation to the knee joint is associated with promising short- and long-term improvement of both pain and function in patients with chronic knee pain.29 Another recent comprehensive systematic review and meta-analysis reported that RFA techniques (conventional or cooled) and pulsed RF neuromodulation can improve knee pain for up to 6 months, with no statistically significant difference between the three RF modalities in pain relief.30
With regards to patient-relevant outcomes of genicular RFA, a multi centre open-label randomised controlled trial found that 74.1% of patients who underwent cooled RFA treatment (4 mm/18G active tip, 60°C for 150 s) under fluoroscopy achieved a ≥50% reduction in pain at 6 months after RFA, compared with only 16.2% of patients who received intra-articular steroid injections. The study also demonstrated that cooled RFA had favourable outcomes in improving function and enhancing the overall quality of life for patients with knee pain secondary to degenerative osteoarthritis.31 In another RCT comparing cooled RFA with single intra-articular hyaluronic acid injection, 71% of subjects in the cooled RF group (the authors reported using 60°C for 150 s for the procedure without specifying the active RF needle tip size) had a ≥50% reduction in pain at 6 months compared with 38% in the hyaluronic acid group.32 It is worth mentioning that the authors of this trial targeted four nerves (genicular nerves and medial retinacular nerve) whereas Davis and colleagues targeted three nerves and both studies showed comparable results.31
A prospective observational study of the long-term outcomes of cooled RF reported ≥50% pain relief at 18 months in 12 subjects out of 25.33 These data support the use of cooled RF as a safe modality that can provide long-term pain relief and functional improvement. A recent RCT found that both cooled RF (4 mm/17G active tip, 150 s) and conventional RF (10 mm/16G active tip, 90 s) targeting the genicular nerves under fluoroscopy guidance provide significant long-term improvement in pain and function with no difference between the two RF modes.20 A recent pilot study comparing cooled RF (4 mm/18G active tip, 60°C for 150 s) with conventional monopolar RF (10 mm/18G active tip, 80°C for 90 s) showed that the proportion of patients experiencing >50% pain relief was 17% in the monopolar RF group and 33% in the cooled RF group, with no difference between the groups. These findings support that both monopolar and cooled RF can significantly improve knee pain secondary to osteoarthritis and persistent pain after TKA.34 It is notable that this pilot study included patients with anterior knee pain secondary to either osteoarthritis or persistent pain after TKA that failed to respond to conservative treatment. In addition, there was no diagnostic block before the ablation procedures, which could have affected the outcomes of the study. Table 2 summarises key findings of selected published studies.
Table 2.
Summary of selected studies published in the last 10 yrs on radiofrequency ablation of innervation to the knee joint. All included studies targeted the genicular nerves under fluoroscopy except Vanneste 2023 (genicular nerves under US and fluoroscopy).34 CS-R, case series-retrospective; EQ-5D-3L, EuroQol-5 Dimensions- 3 Level; GPE, Global Perceived Effect; HADS, Hospital Anxiety and Depression Scale; MQS III, Medication Quantification Scale III; NRS, Numerical Rating Scale; OKS, Oxford Knee Score; PCS, Pain Catastrophizing Scale; PGIC, Patient Global Impressions Scale; RCT, randomised controlled trial; RFA, radiofrequency ablation; US, ultrasound; VAS, Visual Analogue Scale; WOMAC, Western Ontario and McMaster Universities Arthritis Index.
| Author, yr; type of study (number of participants) | RFA mode | Outcome measures | Follow-up time points | Conclusions |
|---|---|---|---|---|
| Bellini 2015; CS-R (9)35 | Cooled (details of the procedure were not reported by the authors) | VAS, WOMAC, patient satisfaction | 12 Months | Significant reduction in pain scores and WOMAC at 1, 3, 6 and 12 months after procedure |
| Davis 2018; RCT (151)31 | Cooled (4 mm/18G active tip, 60°C for 150 s) vs intra-articular injection of steroid | NRS, OKS, GPE, use of analgesics | 1, 3 And 6 months | Cooled RFA improved pain, function, and overall quality of life for patients with knee OA more compared with intra-articular steroid injection at 6 months |
| Chen 2020; RCT (175)32 | Cooled vs intra-articular injection of hyaluronic acid (authors reported using 60°C for 150 s without specifying the active tip size) | NRS, WOMAC, GPE | 1, 3 And 6 months | Cooled RFA showed favourable outcomes and improved both pain and function more compared with intra-articular hyaluronic acid injection at 6 months |
| Vallejo 2023; RCT (75)20 | Cooled (4 mm/17G active tip, 150 seconds) vs monopolar (10 mm/16G active tip, 90 s) | VAS, WOMAC, OKS, GPE | 4, 12, 24 And 52 weeks | Both cooled RF and conventional RF resulted in long-term pain relief and improvement of function and quality of life with no difference in long-term outcomes between the two modalities |
| Vanneste 2023; Pilot RCT (47)34 | Cooled (4 mm/18G active tip, 60°C for 150 s) vs monopolar (10 mm/18G active tip, 80°C for 90 s) | NRS, OKS, PGIC, EQ-5D-3L, HADS, PCS, MQS III |
1, 3 And 6 months | Both conventional and cooled RF improved pain secondary to knee osteoarthritis and after knee arthroplasty with no significant difference between the two modalities |
Factors associated with improved outcomes after genicular RFA
A retrospective study assessing clinical and technical factors that may contribute to superior outcomes in knee RFA found several factors were associated with better results.36 Better outcomes were observed in patients without concurrent mental health conditions, those not on opioids, patients with milder severity of knee arthritis and those who reported lower pre-procedure pain scores. A comprehensive review reported that RFA is associated with significant pain relief and functional improvement that can last up to 12 months.19 In addition, certain technical factors were linked to better results, including using cooled RFA instead of pulsed or conventional RFA, using strategies to create larger lesions (using 18G or larger electrodes with a 10-mm active tip, creating multiple lesions), targeting more than three nerves23 and patients reporting >80% pain relief after diagnostic blocks. Two different RCTs have demonstrated that cooled RF is associated with long-term improvements in both pain and functionality.30,31
Ongoing research
An ongoing study is evaluating whether a more aggressive and precise lesioning approach (nine or 10 nerves with large electrodes and long heating times) proves efficacious compared with sham lesioning, and more effective than intra-articular injections, in a pragmatic study in patients with knee osteoarthritis (Sequenced Strategy for Improving Outcomes in People with Knee Osteoarthritis Pain [SKOAP]; ClinicalTrials.gov Identifier: NCT04504812).37
Conclusions and directions for future research
Radiofrequency ablation for denervation of the anterior knee joint offers patients with refractory knee pain a promising outcome in terms of improving pain and functionality for up to 3–12 months.18 A survey conducted by the American Society of Pain and Neuroscience (ASPN) to assess common practices of genicular nerve RFA among experienced practitioners, found a high degree of consensus regarding targeting the three nerves proposed by Choi and colleagues.3 It also sheds light on the lack of standardisation in several aspects, including the choice and volume of local anaesthetic for diagnostic blocks and the number of blocks performed. Although most interventionalists use fluoroscopy-guided procedures, there is no consensus on the selection of needle gauge, the number of lesions made at each target, temperature settings and the duration of lesioning.16
Previous trials have demonstrated better outcomes compared with intra-articular injections and amongst patients experiencing persistent pain after TKA.19 Based on the current understanding of the neuroanatomical variation of knee innervation, future research is needed to reach a consensus on neural targets for ablation, selection criteria, and evidence for the comparative effectiveness of various RFA and non-RFA modalities.
Declaration of interests
The authors declare that they have no conflicts of interest.
MCQs
The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.
Biographies
Abeer Alomari MBBS is a senior fellow in pain medicine at the University of Toronto. She is a physiatrist and completed a 2-yr fellowship in interventional pain medicine with the Department of Physical Medicine and Rehabilitation at the University Health Network, Toronto. Her major clinical and research interests are interventional musculoskeletal pain management techniques including radiofrequency ablation.
Anuj Bhatia MD PhD FRCA FFPMRCA FRCPC is a professor in anesthesia and pain medicine at Toronto Western Hospital and the director of the Comprehensive Integrated Pain Program at University Health Network, Toronto, Canada. He is the chair of the Neuropathic Pain Special Interest Group of the Canadian Pain Society.
Matrix codes: 1D02, 2E03, 3E00
References
- 1.Felson D.T., Naimark A., Anderson J., et al. The prevalence of knee osteoarthritis in the elderly. The Framingham Osteoarthritis Study. Arthritis Rheum. 1987;30:914–918. doi: 10.1002/art.1780300811. [DOI] [PubMed] [Google Scholar]
- 2.Jordan J.M., Helmick C.G., Renner J.B., et al. Prevalence of knee symptoms and radiographic and symptomatic knee osteoarthritis in African Americans and Caucasians: the Johnston County osteoarthritis project. J Rheumatol. 2007;34:172–180. [PubMed] [Google Scholar]
- 3.Choi W.J., Hwang S.J., Song J.G., et al. Radiofrequency treatment relieves chronic knee osteoarthritis pain: a double-blind randomized controlled trial. Pain. 2011;152:481–487. doi: 10.1016/j.pain.2010.09.029. [DOI] [PubMed] [Google Scholar]
- 4.Roberts S.L., Stout A., Dreyfuss P. Review of knee joint innervation: implications for diagnostic blocks and radiofrequency ablation. Pain Med. 2020;21:922–938. doi: 10.1093/pm/pnz189. [DOI] [PubMed] [Google Scholar]
- 5.Tran J., Peng P.W.H., Lam K., et al. Anatomical study of the innervation of anterior knee joint capsule: implication for image-guided intervention. Reg Anesth Pain Med. 2018;43:407–414. doi: 10.1097/AAP.0000000000000778. [DOI] [PubMed] [Google Scholar]
- 6.Gardner E. The innervation of the knee joint. Anat Rec. 1948;101:109–130. doi: 10.1002/ar.1091010111. [DOI] [PubMed] [Google Scholar]
- 7.Fonkoue L., Behets C., Kouassi J.K., et al. Distribution of sensory nerves supplying the knee joint capsule and implications for genicular blockade and radiofrequency ablation: an anatomical study. Surg Radiol Anat. 2019;41:1461–1471. doi: 10.1007/s00276-019-02291-y. [DOI] [PubMed] [Google Scholar]
- 8.Kennedy J.C., Alexander I.J., Hayes K.C. Nerve supply of the human knee and its functional importance. Am J Sports Med. 1982;10:329–335. doi: 10.1177/036354658201000601. [DOI] [PubMed] [Google Scholar]
- 9.Horner G., Dellon A.L. Innervation of the human knee joint and implications for surgery. Clin Orthop Relat Res. 1994;301:221–226. [PubMed] [Google Scholar]
- 10.Runge C., Moriggl B., Borglum J., Bendtsen T.F. The spread of ultrasound-guided injectate from the adductor canal to the genicular branch of the posterior obturator nerve and the popliteal plexus: a cadaveric study. Reg Anesth Pain Med. 2017;42:725–730. doi: 10.1097/AAP.0000000000000675. [DOI] [PubMed] [Google Scholar]
- 11.Tran J., Peng P.W.H., Gofeld M., et al. Anatomical study of the innervation of posterior knee joint capsule: implication for image-guided intervention. Reg Anesth Pain Med. 2019;44:234–238. doi: 10.1136/rapm-2018-000015. [DOI] [PubMed] [Google Scholar]
- 12.Fonkoue L., Behets C.W., Steyaert A., et al. Accuracy of fluoroscopic-guided genicular nerve blockade: a need for revisiting anatomical landmarks. Reg Anesth Pain Med. 2019;44:950–958. doi: 10.1136/rapm-2019-100451. [DOI] [PubMed] [Google Scholar]
- 13.Kim D.H., Myung-Su L., Lee S., et al. A prospective randomized comparison of the efficacy of ultrasound- vs fluoroscopy-guided genicular nerve block for chronic knee osteoarthritis. Pain Physician. 2019;22:139–146. [PubMed] [Google Scholar]
- 14.Sari S., Aydin O.N., Turan Y., et al. Which imaging method should be used for genicular nerve radio frequency thermocoagulation in chronic knee osteoarthritis? J Clin Monit Comput. 2017;31:797–803. doi: 10.1007/s10877-016-9886-9. [DOI] [PubMed] [Google Scholar]
- 15.Dağistan G., Gönüllü E. Ultrasound vs. fluoroscopic guidance in genicular nerve radiofrequency thermocoagulation for chronic knee pain: which one is the future? Eur Rev Med Pharmacol Sci. 2023;27:7073–7080. doi: 10.26355/eurrev_202308_33280. [DOI] [PubMed] [Google Scholar]
- 16.Abd-Elsayed A., Strand N., Gritsenko K., et al. Radiofrequency ablation for the knee joint: a survey by the American society of pain and neuroscience. J Pain Res. 2022;15:1247–1255. doi: 10.2147/JPR.S342653. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.McCormick Z.L., Reddy R., Korn M., et al. A prospective randomized trial of prognostic genicular nerve blocks to determine the predictive value for the outcome of cooled radiofrequency ablation for chronic knee pain due to osteoarthritis. Pain Med. 2018;19:1628–1638. doi: 10.1093/pm/pnx286. [DOI] [PubMed] [Google Scholar]
- 18.Ajrawat P., Radomski L., Bhatia A., et al. Radiofrequency procedures for the treatment of symptomatic knee osteoarthritis: a systematic review. Pain Med. 2020;21:333–348. doi: 10.1093/pm/pnz241. [DOI] [PubMed] [Google Scholar]
- 19.Jamison D.E., Cohen S.P. Radiofrequency techniques to treat chronic knee pain: a comprehensive review of anatomy, effectiveness, treatment parameters, and patient selection. J Pain Res. 2018;11:1879–1888. doi: 10.2147/JPR.S144633. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Vallejo R., Benyamin R., Orduña-Valls J., et al. A randomized controlled study of the long-term efficacy of cooled and monopolar radiofrequency ablation for the treatment of chronic pain related to knee osteoarthritis. Interv Pain Medicine. 2023;2 doi: 10.1016/j.inpm.2023.100249. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.McCormick Z.L., Cohen S.P., Walega D.R., et al. Technical considerations for genicular nerve radiofrequency ablation: optimizing outcomes. Reg Anesth Pain Med. 2021;46:518–523. doi: 10.1136/rapm-2020-102117. [DOI] [PubMed] [Google Scholar]
- 22.McCormick Z.L., Korn M., Reddy R., et al. Cooled radiofrequency ablation of the genicular nerves for chronic pain due to knee osteoarthritis: six-month outcomes. Pain Med. 2017;18:1631–1641. doi: 10.1093/pm/pnx069. [DOI] [PubMed] [Google Scholar]
- 23.Fonkoue L., Behets C.W., Steyaert A., et al. Current versus revised anatomical targets for genicular nerve blockade and radiofrequency ablation: evidence from a cadaveric model. Reg Anesth Pain Med. 2020;45:603–609. doi: 10.1136/rapm-2020-101370. [DOI] [PubMed] [Google Scholar]
- 24.Sperry B.P., Conger A., Kohan L., et al. A proposed protocol for safe radiofrequency ablation of the recurrent fibular nerve for the treatment of chronic anterior inferolateral knee pain. Pain Med. 2021;22:1237–1241. doi: 10.1093/pm/pnaa291. [DOI] [PubMed] [Google Scholar]
- 25.Beckwith M., Cushman D., Clark T., et al. Radiofrequency ablation of the infrapatellar branch of the saphenous nerve for the treatment of chronic anterior inferomedial knee pain. Pain Med. 2023;24:150–157. doi: 10.1093/pm/pnac108. [DOI] [PubMed] [Google Scholar]
- 26.Forero M., Olejnik L.J., Stager S.C. Six-target radiofrequency ablation of the genicular nerve for the treatment of chronic knee pain. Reg Anesth Pain Med. 2023 doi: 10.1136/rapm-2023-104643. Published online ahead of print June 14. [DOI] [PubMed] [Google Scholar]
- 27.Lash D., Frantz E., Hurdle M.F. Ultrasound-guided cooled radiofrequency ablation of the genicular nerves: a technique paper. Pain Manag. 2020;10:147–157. doi: 10.2217/pmt-2019-0067. [DOI] [PubMed] [Google Scholar]
- 28.Fonkoue L., Stoenoiu M.S., Behets C.W., et al. Validation of a new protocol for ultrasound-guided genicular nerve radiofrequency ablation with accurate anatomical targets: cadaveric study. Reg Anesth Pain Med. 2021;46:210–216. doi: 10.1136/rapm-2020-101936. [DOI] [PubMed] [Google Scholar]
- 29.Orhurhu V., Urits I., Grandhi R., et al. Systematic review of radiofrequency ablation for management of knee pain. Curr Pain Headache Rep. 2019;23:1–13. doi: 10.1007/s11916-019-0792-y. [DOI] [PubMed] [Google Scholar]
- 30.Chou S.H., Shen P.C., Lu C.C., et al. Comparison of efficacy among three radiofrequency ablation techniques for treating knee osteoarthritis: a systematic review and meta-analysis. Int J Environ Res Public Health. 2021;18:7424. doi: 10.3390/ijerph18147424. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31.Davis T., Loudermilk E., DePalma M., et al. Prospective, multicenter, randomized, crossover clinical trial comparing the safety and effectiveness of cooled radiofrequency ablation with corticosteroid injection in the management of knee pain from osteoarthritis. Reg Anesth Pain Med. 2018;43:84–91. doi: 10.1097/AAP.0000000000000690. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32.Chen A.F., Khalouf F., Zora K., et al. Cooled radiofrequency ablation compared with a single injection of hyaluronic acid for chronic knee pain: a multicenter, randomized clinical trial demonstrating greater efficacy and equivalent safety for cooled radiofrequency ablation. J Bone Joint Surg Am. 2020;102:1501–1510. doi: 10.2106/JBJS.19.00935. [DOI] [PubMed] [Google Scholar]
- 33.Hunter C., Davis T., Loudermilk E., et al. Cooled radiofrequency ablation treatment of the genicular nerves in the treatment of osteoarthritic knee pain: 18- and 24-month results. Pain Pract. 2020;20:238–246. doi: 10.1111/papr.12844. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34.Vanneste T., Belba A., Kallewaard J.W., et al. Comparison of cooled versus conventional radiofrequency treatment of the genicular nerves for chronic knee pain: a multicenter non-inferiority randomized pilot trial (COCOGEN trial) Reg Anesth Pain Med. 2023;48:197–204. doi: 10.1136/rapm-2022-104054. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35.Bellini M., Barbieri M. Cooled radiofrequency system relieves chronic knee osteoarthritis pain: the first case series. Anesthesiol Intens Ther. 2015;47:30–33. doi: 10.5603/AIT.2015.0003. [DOI] [PubMed] [Google Scholar]
- 36.Chen Y., Vu T.H., Chinchilli V.M., et al. Clinical and technical factors associated with knee radiofrequency ablation outcomes: a multicenter analysis. Reg Anesth Pain Med. 2021;46:298–304. doi: 10.1136/rapm-2020-102017. [DOI] [PubMed] [Google Scholar]
- 37.Cohen S.P., Mishra P., Wallace M., et al. Emperor’s nakedness exposed: unmasking fairytales for genicular nerve radiofrequency ablation in knee osteoarthritis. Reg Anesth Pain Med. 2023;48:193–195. doi: 10.1136/rapm-2022-104319. [DOI] [PubMed] [Google Scholar]