How to Do Knee Genicular Nerve Radiofrequency Ablation

By Dr Debjyoti Dutta, 

Asian Pain Academy

Chronic knee pain is one of the most common problems encountered in a pain clinic. Although osteoarthritis is often the underlying pathology, the pain experienced by the patient is not simply a reflection of the radiographic severity of osteoarthritis. In selected patients, targeting the sensory innervation of the knee with radiofrequency treatment can provide meaningful pain relief and improve function.

In this article, I will discuss HOW TO DO KNEE GENICULAR NERVE RADIOFREQUENCY ABLATION, with particular emphasis on patient selection, relevant anatomy, imaging, needle placement, lesioning, and the practical points that influence the outcome of the procedure.

Genicular nerve radiofrequency ablation has evolved considerably over the last few years. The traditional three-target technique remains widely used, while newer anatomical studies and clinical techniques have introduced modified target locations and additional targets. Therefore, choose the technique based on the clinical situation, available imaging guidance, operator experience, and anatomical understanding rather than following a single rigid protocol.

When Should We Consider Knee Genicular Nerve Radiofrequency Ablation?

The typical patient is someone with chronic knee pain, most commonly related to knee osteoarthritis, who has not obtained adequate relief from appropriate conservative treatment.

I generally consider the procedure in a patient who has:

• Chronic knee pain affecting daily activities

• Clinical and/or radiological evidence of knee osteoarthritis

• Persistent pain despite appropriate conservative treatment

• Significant functional limitation

• Unsuitability for knee replacement, or a desire to postpone surgery

• Persistent pain despite other non-operative interventions

The decision should not be based on the X-ray alone. A patient with severe radiographic osteoarthritis may have relatively little pain, while another patient with modest radiographic changes may experience severe pain.

Therefore, the indication for genicular nerve radiofrequency ablation is the patient's pain and disability, not the X-ray grade alone.

Genicular nerve RFA has been studied most extensively for chronic knee osteoarthritis pain, although it is also being investigated and used selectively for persistent postsurgical knee pain. The evidence for post-total-knee-arthroplasty pain is less mature and should be interpreted accordingly.

HOW TO DO KNEE GENICULAR NERVE RADIOFREQUENCY ABLATION: Understanding the Anatomy

The genicular nerves are articular branches derived primarily from branches of the femoral, tibial, and common peroneal nerves. They provide sensory innervation to portions of the knee capsule.

The three traditional targets are:

1. Superior medial genicular nerve (SMGN)

2. Superior lateral genicular nerve (SLGN)

3. Inferior medial genicular nerve (IMGN)

These nerves are not always located exactly where we expect them to be. Their course can vary, and this is one reason why the technical details of RFA matter.

The nerve itself is usually not visualised directly with fluoroscopy. Instead, we use reproducible osseous landmarks and, when using ultrasound, the accompanying vascular structures to identify the target region.

This is an important concept: we are not simply putting the RF cannula "somewhere near the condyle." We are trying to place the active tip in the region where the articular nerve is most likely to run.

Patient Preparation for Knee Genicular Nerve Radiofrequency Ablation

Before the procedure, I reassess the diagnosis and document the baseline pain and functional status.

Useful baseline parameters include:

• Numeric Rating Scale (NRS)

• Walking tolerance

• Stair-climbing ability

• Sleep disturbance

• Requirement for analgesic medication

• Patient-specific functional limitation

• WOMAC or KOOS, when appropriate

• 
  

The patient's expectations should also be discussed.

I explain that genicular nerve RFA is a pain-modulating procedure. It does not reverse osteoarthritis, regenerate cartilage, correct deformity, or stop the progression of joint degeneration.

The purpose is to reduce pain sufficiently to allow the patient to walk better, exercise, participate in rehabilitation, and improve quality of life.

Equipment Required

For conventional thermal RFA, the basic equipment includes:

• RF generator

• Appropriate RF cannula

• RF electrode

• Ultrasound and/or fluoroscopy

• Sterile preparation and draping equipment

• Local anaesthetic

• Monitoring equipment

• Resuscitation equipment appropriate for an interventional pain procedure

The exact cannula gauge, active tip length, temperature, and lesion duration depend on the RF system and technique being used.

Conventional and cooled RF systems create lesions of different geometries, so the technique should always follow the characteristics and recommendations of the particular system being used. Comparative clinical studies have used both conventional and cooled RF for the traditional three genicular targets.

Positioning for Knee Genicular Nerve Radiofrequency Ablation

The patient is generally positioned supine.

The knee may be kept in slight flexion, usually around 10–30 degrees, depending on the imaging technique and operator preference.

A small amount of flexion can make the relevant bony landmarks easier to visualise and may improve patient comfort.

The procedure should be performed under appropriate monitoring with strict aseptic precautions.

Sedation is usually unnecessary. I prefer the patient to remain communicative whenever possible because patient feedback can be useful during needle placement and stimulation.

Fluoroscopy-Guided Knee Genicular Nerve Radiofrequency Ablation

Fluoroscopy provides excellent visualisation of the bony landmarks and remains a widely used technique.

The three traditional targets are approached individually.

Superior Medial Genicular Nerve

The target is located around the transition between the distal femoral shaft and the medial femoral condyle.

The important principle is to identify the shaft-condyle junction rather than simply targeting the most prominent portion of the medial femoral condyle.

The RF cannula is advanced toward the osseous target under appropriate fluoroscopic views.

Once the cannula reaches the intended bony position, the final position should be confirmed in more than one plane where appropriate.

Superior Lateral Genicular Nerve

The superior lateral genicular nerve is targeted around the junction of the distal femoral shaft and lateral femoral condyle.

Careful attention is required because the lateral side has important vascular structures in the vicinity.

The needle should be advanced under controlled imaging rather than using a blind deep trajectory.

Inferior Medial Genicular Nerve

The inferior medial genicular nerve is targeted around the transition between the proximal tibial shaft and the medial tibial condyle.

Again, the objective is to position the active electrode in the appropriate periosteal region corresponding to the expected course of the nerve.

The relationship between the bony target and nearby vessels should be carefully considered.

Ultrasound-Guided Knee Genicular Nerve Radiofrequency Ablation

Ultrasound provides an important advantage because the genicular vessels can often be identified and used as an additional anatomical landmark.

A practical ultrasound approach is to first identify the relevant femoral or tibial bony junction in a longitudinal orientation and then rotate the probe to obtain the transverse view.

The genicular vessels can often be seen adjacent to the bone. The nerve itself may be difficult to visualise, and therefore the technique relies on a combination of:

• Bony landmarks

• Genicular vessels

• Soft-tissue anatomy

• Needle trajectory

An in-plane needle approach allows continuous visualisation of the needle shaft and tip.

The needle is advanced toward the periosteal surface at the target location.

One important advantage of ultrasound is that it allows direct visualisation of vascular structures and may therefore help reduce inadvertent vascular puncture. Ultrasound and fluoroscopy can also be combined, with ultrasound assisting needle placement and fluoroscopy confirming the final bony position.

HOW TO DO KNEE GENICULAR NERVE RADIOFREQUENCY ABLATION: Needle Placement

Once the skin has been prepared and local anaesthesia administered, the RF cannula is advanced toward the selected genicular target.

I consider three things particularly important:

1. The needle tip should be at the correct bony level

Being too proximal or too distal can place the electrode away from the expected nerve location.

2. The electrode orientation matters

The active tip should be positioned in a manner that maximises the likelihood of intersecting the nerve.

Remember that an RF lesion is three-dimensional. The electrode does not need to physically touch the nerve, but it needs to be sufficiently close to create an effective thermal lesion.

3. Confirm the final position

A single fluoroscopic projection can sometimes be misleading. Appropriate confirmation in another plane is useful, particularly when the bony anatomy is difficult to interpret.

The modern literature has highlighted that traditional target descriptions may not always correspond to the optimal location of the nerve, and modified targeting strategies are being investigated.

Sensory and Motor Stimulation

Stimulation protocols vary according to the technique and equipment being used.

Sensory stimulation can be used to assess proximity to the intended sensory structure, while motor stimulation may help identify an undesired proximity to motor nerves.

For example, one published clinical protocol used sensory stimulation at 50 Hz and motor stimulation at 2 Hz before proceeding with lesioning.

I consider stimulation an adjunct rather than a substitute for good anatomical needle placement.

A technically poor needle position cannot be corrected simply by relying on stimulation.

Local Anaesthesia Before Radiofrequency Lesioning

After confirming the final cannula position, a small volume of local anaesthetic may be administered at the target.

The volume should be kept appropriate for the procedure because excessive injectate can potentially spread away from the intended target.

The exact drug concentration and volume depend on the clinical setting and operator preference.

Conventional Thermal Radiofrequency Lesioning

Once the final position has been confirmed, thermal RF lesioning is performed according to the generator and electrode system being used.

A commonly described conventional RF protocol uses approximately:

• 80°C

• 90 seconds

for each target.

However, these settings should not be treated as universal rules. Different electrodes, generators, active-tip lengths, and lesion strategies may require different settings.

Published comparative studies have used 80°C for 90 seconds for conventional RF, while cooled RF systems use different temperature and duration parameters because the mechanism of lesion creation is different.

The important principle is to understand the RF system being used rather than memorising one temperature-time combination.

Cooled Radiofrequency Ablation

Cooled RF creates a larger lesion around the electrode because cooling permits the electrode to deliver energy while limiting the temperature immediately adjacent to the probe.

This may be advantageous when there is uncertainty regarding the precise location of a small articular nerve.

However, cooled RF is not simply "better conventional RF." It creates a 4 to 5 times larger lesion geometry and has its own technical requirements.

A commonly described cooled RF protocol uses approximately:

• 60°C

• 120 seconds

Clinical trials have compared conventional and cooled RF, and both approaches remain part of contemporary genicular nerve RFA practice.

Should We Always Perform a Diagnostic Genicular Nerve Block?

This remains an area of discussion.

Historically, many clinicians performed a diagnostic genicular nerve block before proceeding to RFA. The logic is straightforward: if anaesthetising the presumed pain-mediating nerves produces substantial temporary pain relief, neurotomy should theoretically be more likely to work.

However, the evidence regarding prognostic blocks is not uniform.

Recent discussions have questioned whether a prognostic block should be mandatory before genicular RFA, and at least one randomised study protocol has performed RFA without a preceding prognostic block.

My approach is to use the diagnostic block as one component of patient selection rather than considering it an absolute prerequisite in every patient.

The clinical picture, degree of pain, functional limitation, diagnosis, imaging, previous treatment response, and patient expectations all matter.

How Many Genicular Nerves Should We Treat?

The traditional approach is to treat three nerves:

• Superior medial

• Superior lateral

• Inferior medial

This remains a practical and widely used approach.

However, anatomical studies have demonstrated considerable variation in genicular nerve anatomy. Consequently, newer approaches have proposed modified target locations and additional targets.

Six-target RFA and other expanded techniques are being investigated, but these approaches should not automatically replace the established three-target technique.

For someone learning the procedure, I would recommend first becoming extremely comfortable with the anatomy, imaging, and technical execution of the conventional three-target technique.

Common Technical Mistakes in Knee Genicular Nerve Radiofrequency Ablation

Mistake 1: Treating the X-ray instead of the patient

Radiographic osteoarthritis is not synonymous with pain.

Always establish a convincing clinical diagnosis before planning RFA.

Mistake 2: Targeting the most obvious part of the condyle

The target is not simply "the femoral condyle."

The relationship between the shaft and condyle is important. Small differences in needle position can significantly alter the relationship between the active electrode and the nerve.

Mistake 3: Ignoring vascular anatomy

Genicular vessels are close to the expected nerve targets.

Ultrasound can be particularly useful for identifying these vessels before advancing the needle.

Mistake 4: Accepting a single fluoroscopic view

A cannula that appears appropriate in one projection may be poorly positioned in another.

Whenever appropriate, confirm the final position in additional imaging planes.

Mistake 5: Using excessive local anaesthetic

Large volumes may obscure the diagnostic value of the procedure and can spread beyond the intended target.

Mistake 6: Assuming that a technically successful RFA guarantees success

Pain in osteoarthritis is multifactorial.

Synovitis, bone marrow lesions, subchondral pathology, central sensitisation, muscular dysfunction, biomechanical abnormalities, and psychological factors may all contribute.

Genicular nerve RFA addresses only one component of this complex pain system.

Complications of Knee Genicular Nerve Radiofrequency Ablation

Genicular RFA is generally considered a minimally invasive procedure, but it is not without risk.

Potential complications include:

• Local pain after the procedure

• Bruising

• Haematoma

• Infection

• Skin burns

• Temporary paraesthesia

• Neuritis or neuropathic pain

• Vascular injury

• Bleeding

• Incomplete or absent pain relief

Vascular structures should receive particular attention because genicular arteries accompany the relevant anatomical regions.

Good imaging, careful needle advancement, appropriate sterile technique, and proper patient selection are essential for reducing complications.

Post-Procedure Management

The patient should be observed appropriately after the procedure and discharged when clinically stable according to the facility's protocol.

I generally advise patients that:

• Some soreness at the treatment sites is possible.

• Pain relief may not be immediate.

• They should gradually return to activity.

• Rehabilitation should continue.

• Improvement should be assessed over time rather than judged only during the first few days.

The most important objective is not simply a reduction in the NRS score. It is improvement in function.

If the patient's pain decreases but walking, sleep, exercise capacity, and daily activities do not improve, the clinical benefit may be limited.

What Results Should We Expect?

Genicular nerve RFA can provide clinically meaningful pain relief in appropriately selected patients, but the magnitude and duration of benefit vary considerably.

Published studies have demonstrated benefit extending into the medium term, including outcomes around 6–12 months in some patients. However, recent literature has also highlighted substantial heterogeneity between studies and uncertainty regarding the optimal patient-selection and technical protocols.

Therefore, I do not describe genicular RFA to patients as a permanent treatment.

I describe it as a minimally invasive pain-relieving intervention that may provide a window of improved function.

That window can be particularly valuable when it allows the patient to:

• Walk more

• Exercise

• Reduce analgesic dependence

• Improve muscle strength

• Lose weight when appropriate

• Participate in physiotherapy

• Delay or reconsider surgery

Knee Genicular Nerve Radiofrequency Ablation and Total Knee Replacement

Genicular RFA should not be presented as a replacement for total knee arthroplasty in a patient who clearly requires surgery.

For patients with advanced structural disease and appropriate surgical indications, knee replacement remains an important definitive treatment option.

RFA may be considered in selected patients who:

• Are poor surgical candidates

• Wish to delay surgery

• Have significant comorbidities

• Are not ready for surgery

• Have persistent pain despite conservative management

Its role after total knee arthroplasty is also being investigated. The available evidence suggests potential benefit in selected patients with persistent postsurgical pain, but the evidence base remains considerably less robust than that for knee osteoarthritis.

My Practical Approach to Knee Genicular Nerve Radiofrequency Ablation

When I perform HOW TO DO KNEE GENICULAR NERVE RADIOFREQUENCY ABLATION, I try to keep the procedure conceptually simple:

First, make the diagnosis. Second, select the right patient. Third, understand the anatomy. Fourth, identify the target accurately. Fifth, place the electrode correctly. Sixth, create an adequate lesion. Finally, measure the functional outcome.

The quality of the procedure depends much more on these principles than on simply knowing a particular needle angle or RF temperature.

The most important technical skill is the ability to translate three-dimensional anatomy into the imaging plane in front of you.

Conclusion

HOW TO DO KNEE GENICULAR NERVE RADIOFREQUENCY ABLATION is not simply a question of where to put three needles and switch on the RF generator.

Successful treatment begins with appropriate patient selection and continues through accurate anatomical targeting, careful imaging, safe needle placement, appropriate lesion creation, and structured follow-up.

The conventional superior medial, superior lateral, and inferior medial genicular nerve targets remain the foundation of the procedure. At the same time, our understanding of genicular nerve anatomy continues to evolve, and newer targeting strategies may further improve outcomes.

For the pain physician, the goal should not be to perform RFA routinely in every patient with knee osteoarthritis. The goal should be to identify the patient in whom denervation is likely to provide meaningful functional benefit—and then perform the procedure with anatomical precision and technical discipline.

Dr Debjyoti Dutta, 

Asian Pain Academy