New research suggests an unconventional treatment may be just what the doctor ordered for combating the joint pain, stiffness, and swelling of knee osteoarthritis: low-dose radiation treatments.
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Low-dose radiation for osteoarthritis isn’t a new treatment per se; it’s more commonly used outside of the United States. “In some European countries, low-dose radiation has been used for arthritis and other painful conditions for decades,” says Byoung Hyuck Kim, MD, PhD, principal investigator on the trial and an assistant professor of radiation oncology at the Seoul National University College of Medicine and Boramae Medical Center in Korea.
Here’s what the recent study discovered, plus what to know before considering radiation for knee pain.
Low-Dose Radiation Can Have a Big Impact on Knee Pain
For the study, researchers recruited 114 people with mild-to-moderate knee osteoarthritis at three academic centers in Korea. Participants were randomly assigned to receive six sessions of one of the following:
- A very low dose of radiation at 0.3 Gy
- Low-dose radiation at 3 Gy
- A sham treatment where the patients went through the same setup as the others, but the machine didn’t deliver radiation
Gy, short for gray, is a unit that measures the amount of energy from radiation deposited into a unit mass of tissue. Dr. Kim says that a single low dose of radiation for knee pain would be about 5 percent of the dose given for cancer treatment (although cancer dosages can vary by the type of cancer and location).
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During the study period, patients were only allowed to use acetaminophen as needed but could not use other pain relievers.
After four months, 70 percent of participants in the low-dose radiation group had meaningful improvement in at least two of three categories: pain, physical function, and overall assessment of their condition.
By comparison, 42 percent of people in the placebo group and 58 percent of people in the very low-dose group met responder criteria.
Nearly 57 percent of people in the low-dose group had meaningful improvements in pain, stiffness, and how well their knees functioned, compared with about 30 percent in the placebo group.
Radiation Works on Knee Pain a Few Ways
Low-dose radiation therapy is thought to ease knee pain by combating inflammation, says Austin Kirschner, MD, PhD, an associate professor of radiation oncology at Vanderbilt University Medical Center in Nashville, Tennessee. He was senior author of a scientific review published in 2022 on the topic, which found low-dose radiation therapy mutes the ability of immune cells to produce cytokines, proteins that prompt inflammation in the body. “This promotes an anti-inflammatory environment [and] leads to decreased joint inflammation and, consequently, pain relief,” Dr. Kirschner says.
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“It can calm overactive immune and inflammatory signals in the joint, which may reduce pain and stiffness without the side effects of long-term medications,” Kim says.
Radiation Therapy for Osteoarthritis Isn’t New
Osteoarthritis treatment in the United States usually involves medication or surgery, rather than radiation.
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“In the States, there has been reluctance [to use radiation for knee pain] because we didn’t really have a clinical trial comparing low-dose radiation with a placebo, which we have now,” says Janna Andrews, MD, chair of radiation medicine at Phelps Hospital of Northwell Health in Sleepy Hollow, New York.
Orrin Troum, MD, a rheumatologist at Providence Saint John’s Health Center in Santa Monica, California, points out that low-dose radiation for osteoarthritis was used during most of the 20th century. “It fell out of favor when other medicines, like nonsteroidal anti-inflammatory drugs (NSAIDs), came into play,” he says. “There were concerns about the effects of the low-dose radiation, which never really panned out given how low-dose this therapy is.”
Other research has found promise in using low-dose radiation to treat knee pain. A study of about 300 people with knee osteoarthritis published in 2023 found that low-dose radiation cut the risk of disability by 50 percent compared with placebo. After a decade of follow-up, 90 percent of participants in the radiation group had no disability, compared with 80 percent of those who received a placebo.
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Another small study of 65 people with knee osteoarthritis found that participants who received low-dose radiation therapy lowered their pain score rating from 9 out of 10 to a 6. Those in the placebo group had no drop in pain.
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Study Has Strengths and Weaknesses
The study’s sham-controlled design helped to rule out a potential placebo effect, and limiting medications that are stronger than acetaminophen also helped identify radiation as the cause for changes in pain and mobility, Kirschner says.
But Kirschner points out that this study has a relatively short follow-up of just four months. “Long-term efficacy, safety, and imaging-based outcomes are still pending,” he says. The study was also done in a Korean population, so it’s unclear if the treatment will have the same response in other ethnic or healthcare settings, says Kirschner.
How to Deal With Ongoing Knee Pain
If you have knee pain, it’s important to be evaluated by a physician to see if it could be due to osteoarthritis or some other cause. Your doctor will recommend a treatment plan from there, which may include low-dose radiation therapy.
“I’ve been using this for several years with my patients,” says Dr. Troum. “It has had a significant, dramatic impact on some patients.” Troum says he generally notices that the treatment tends to be about 70 percent effective, with results that last up to two years.
Dr. Andrews also uses this treatment on patients with osteoarthritis. “It can be a game changer for patients who aren’t surgical candidates or who aren’t interested in living their lives on pain medication,” she says. “But not too many places in the country offer this. I’ve had patients call me from all over.”
Kirschner says the latest study “adds to a growing body of international evidence” that supports low-dose radiation therapy for osteoarthritis pain, but it’s still not considered a first-line treatment. “It’s not a replacement for exercise or lifestyle measures, but it could become an additional option for carefully selected patients when usual medications or injections are not suitable,” Kim says.
