Authors: Tara Haelle; Lisa Mandl, MD, MPH
Medscape Medical News
Knee osteoarthritis is projected to affect an estimated 642 million people across the globe by the year 2050, and its huge impact on people’s quality of life makes it a major public health problem, according to Lisa Mandl, MD, MPH, an associate professor of medicine at Hospital for Special Surgery (HSS) and Weill Cornell Medicine in New York City. The worldwide increase in incidence is due to multiple factors, including increased longevity, an increase in obesity, and an increase in knee injuries.
“People are being more active, and a lot of people are having knee injuries when they’re younger, which dramatically increases their risk for knee osteoarthritis over the next decades,” Mandl told Medscape Medical News.
The main treatments start with lifestyle modification, including exercise, weight loss, physical therapy, braces, and over-the-counter pain relievers, such as nonsteroidal anti-inflammatory drugs (NSAIDs). But those medications have side effects that can become serious with extended use or may be contraindicated in many people. Steroid injections can offer temporary relief, but the most severe cases may require knee replacement surgery. Many people would prefer to avoid surgery, or it may not be medically appropriate for them, Mandl said.
“In addition, people who don’t walk and don’t move because they have knee pain then gain weight, have high blood pressure, have high cholesterol, and go on to have heart attack, strokes, and even increased mortality because they’re not moving,” Mandl said. “So, knee pain is a major problem, and we need better solutions.”
That need has led to more research in unconventional nonpharmacologic therapies, such as low-dose radiation, genicular artery embolization, and genicular nerve ablation. However, evidence for low-dose radiation is extremely limited, and although there are some promising open label studies of genicular artery embolization, two of three sham-controlled randomized controlled trials showed no benefit.
The evidence is substantially stronger for genicular nerve ablation. This procedure is FDA-approved for pain relief, and Mandl has begun referring patients for this treatment at HSS. Mandl spoke with Medscape about this treatment, which has been gaining interest in recent years.
Your institution has begun offering radiofrequency genicular nerve ablation. Can you describe what that involves?
Radiofrequency ablation is a minimally invasive procedure that’s FDA-approved for treatment of chronic pain. First, the doctor uses either ultrasound or fluoroscopy to identify the three major nerves that go around the outside of the knee. Then a metal probe, similar to the tines of a fork, is inserted that uses heat to disrupt the nerve so that it stops working. We know not all pain in the knee is necessarily from inside. It’s really a “whole organ”; this therapy specifically targets knee nerves that surround the knee joint.
It’s just a sensory nerve, not a motor nerve, so when the nerve around the knee doesn’t work anymore, it can lead to decreased pain. The whole point is to damage the nerve, but you don’t want to damage the tissues around it, so that’s why it’s done very carefully with imaging.
What is the experience like for the patient?
I refer patients to our interventional radiology suite, and the whole visit takes a couple hours. It’s definitely more invasive than a knee aspiration, but it’s not like having surgery. The actual procedure takes about a half hour, but the visit requires time for the patient to lay down, undergo the imaging to find the nerves, freeze the area, do the first nerve, and then do the second and third ones. It is a little painful, so before the actual procedure, lidocaine is used to freeze the area before inserting the probe. It can be a little uncomfortable afterwards, so people go home taking some over-the-counter pain relievers like acetaminophen or NSAIDs.
How long has this therapy been around and why isn’t it used more often for knee osteoarthritis?
The technique has been used since the 1960s. Ablation is used a lot for back pain, such as pain from facet joints. So, while the technology has been around for decades, it’s been used more consistently for knee pain since 2010. Ablation can also be used to treat chronic knee pain after knee replacement. Part of the challenge of offering it is that you need someone with the skillset to do it — either an interventional radiologist, an anesthesiologist, or a physiatrist who’s trained in the procedure — and you need the facilities.
We also need more studies to better understand in whom it works best. We need to be able to better phenotype the patients, because it does not help everyone. For example — and these numbers are not exact — if you give it to 100 people and in half of them it works wonderfully, and in the other half it doesn’t, it’s discouraging. But, if we could identify which 50 patients it will work in, that would be great. Also, although Medicare does cover it, other insurances do not always cover it. So, if your insurance will not cover it, I think people are much less likely to do it.
How long does the pain relief last in those who respond to it?
In most people, the evidence shows it lasts 3 to 6 months, 12 months if you’re lucky. That’s based primarily on a 2025 meta-analysis of 25 trials with a little over 2000 patients. Some people get it done again. We do know that the more severe the osteoarthritis is, the less likely the patient is responsive. But we need better predictors to pinpoint in whom it will work best, why it lasts, and why it doesn’t last. The placebo trials show less benefit than the open-label trials, but this procedure can decrease pain, and it really can work from 6 months to a year.
What questions do patients typically have about the procedure before they decide to do it?
They ask whether it will hurt and how long they will be sore. They want to know how long it will last and whether the doctor thinks it will work for them. They also ask, “Will this stop me getting a knee replacement?” If it can decrease the pain enough that the patient can start walking more, lose weight, and strengthen the muscles around their knee, it might improve their pain enough that they don’t need a knee replacement, but there’s no data on that yet. The risk of side effects is very, very low. Some aching or swelling afterwards for a day or two are really the main things. You can burn some of the tissue around the nerve, but that’s very uncommon, especially when it’s done under imaging by a skilled practitioner.
There are certain contraindications that I leave up to the interventional radiologist to determine. For example, some people have poor healing, or if they have lots of skin ulcers, this might not be for them. If you have infection in your knees or infections around the area, you wouldn’t do it. But many people would qualify for it, and those who want to do it are often older people who can’t take or have high risks with oral medications and who don’t want surgery.