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Peripheral Nerve Stimulation of Genicular Nerves in the Treatment of Chronic Knee Pain from Osteoarthritis

Authors:

Darien McNeill, MD, Resident
Jason Schroeder, MD, Resident
Brea Willeford, DO, Fellow
Alethia Sellers, MD, CMQ, Associate Professor

Department of Anesthesiology and Perioperative Medicine
The University of Alabama at Birmingham, Heersink School of Medicine

Introduction:

According to the Centers for Disease Control and Prevention, an estimated 20.9% of adults (51.6 million persons) in the United States suffered from chronic pain during 2021. Due to the increasing prevalence of chronic pain in the setting of an ongoing opioid crisis, research into non-opioid modalities for management has become more important than ever. Neuromodulation is a potential avenue by which physicians may confront this concern.

The concept of neuromodulation involves the alteration of activity in the central, peripheral, or autonomic nervous system with the use of electricity.1 Peripheral nerve stimulation (PNS), a procedure which utilizes this concept, has demonstrated utility in the treatment of both acute postoperative and chronic pain seen in conditions such as knee osteoarthritis.2 PNS involves the use of electrical currents passed through an implanted wire to target specific nerves. We describe the case of a patient with chronic knee pain who previously saw limited improvement with multiple conservative modalities including genicular nerve blocks and developed a significant reduction in pain level with peripheral nerve stimulation.

Case Report:

A 71-year-old female with history of systemic lupus erythematosus presented to the pain clinic with bilateral knee pain, right greater than left. Her pain had been present for years, mostly in the anterior knee region without radiation. Her pain had progressed to the point where she was utilizing a walker for home and community ambulation. Her SLE was being treated with dapsone and methotrexate. She used celecoxib for “flare-ups” of knee intra-articular pain. Other relevant surgical history included posterior instrumented fusion of C1-C2 5 years prior for cervical myelopathy. X-ray of the right knee revealed moderate tricompartmental osteoarthrosis centered at the lateral compartment with a trace knee effusion. There was no evidence that articular erosions were present.

At the time of her presentation to the pain clinic, she had undergone 5 years of various treatments for her knee pain including physical therapy, intra-articular corticosteroid and hyaluronic acid injections, and genicular nerve blocks, all of which provided partial or inadequate pain relief. She had recently been seen by Sports Medicine orthopedics and was offered total knee arthroplasty (TKA). In an effort to avoid surgery, she presented with interest in PNS treatment.

She presented twice to the procedure room for placement of PNS leads. Fluoroscopic guidance was used to place the PNS lead in proximity to the right superior lateral genicular nerve and three weeks later at the site of the right medial genicular nerve. The final locations were confirmed with electrical stimulation and documented with imaging. At 30-day follow up evaluation, there was a 50% reduction of pain with increased functional capacity and increased tolerance of physical therapy. She reported a threshold around 70 Hz where she would feel an uncomfortable “electric shock,” however, keeping the settings around 60Hz provided pain relief. These benefits were continued through 60-day follow up evaluation with 60% pain reduction, at which time the PNS leads were removed per protocol. At follow up 113 days from initial placement and 53 days from removal of the leads she continued to report a 60-70% reduction in pain of the right knee. There were no adverse events or outcomes.

Discussion:

Osteoarthritis is the most common cause of chronic knee pain in older adults over the age of 50.5 Typically, patients with long standing symptoms have been managed with a multimodal regimen which may include exercise-based therapy, NSAIDs, bracing, topical agents, diet and activity modifications, corticosteroid injections, and hyaluronic acid injections.6 Those who have pain symptoms refractory to conservative treatment often proceed to surgical intervention involving TKA. PNS offers another option for patients who either want to avoid surgery or are unable to undergo surgery due to medical contraindications. Knee pain may also persist following TKA with some studies demonstrating approximately 20% of patients suffer from chronic postoperative pain.7,8 In these patients, PNS has been utilized with successful management of refractory postoperative symptoms.9

The mechanism of pain relief from PNS remains unknown. It is thought to be based in part to the gate control theory where there is excitation of the dorsal horn interneurons, neurons involved in the processing of pain in the spinal cord, by non-nociceptive Aβ fibers carrying afferents from the site of stimulation.1,10,12 This results in inhibition of the pain signals sent to the brain. Additionally PNS has been shown to decrease hyperalgesia and central sensitization through the reduction of excessive peripheral nociceptive activity centrally.10 There have also been animal studies which have shown release of GABA and other neurotransmitters that reduce hyper-excitability.10 Furthermore there is evidence that PNS can reduce pain through afferent information from mechanical receptors such as golgi tendon organs and muscle spindles as shown in treatment of hemiplegic shoulder pain.11

Although originally studied as an acute postoperative treatment for pain relief, PNS has shown promise with different forms of chronic knee pain.3 Improved outcomes in health-related domains including pain, quality of life, function, and sleep have been demonstrated.4 Case reports and industry reviews have emphasized femoral, sciatic, or saphenous nerves for this indication. Our patient had clinically significant positive outcomes with stimulation of genicular nerves further indicating peripheral nerve stimulation as a promising alternative approach to knee pain treatment.

Conclusion:

PNS treatment of chronic knee pain has shown improvements in pain and function in prior reports. Here we demonstrate clinically positive outcomes through a less common approach targeting the superior medial and lateral genicular nerves.

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