may give real pain relief to people with mild to moderate knee osteoarthritis without major side effects.
Osteoarthritis is the most common form of arthritis, affecting over 32 million adults in the United States alone. It happens when the cartilage that cushions the ends of bones wears down over time, leading to pain, stiffness, and reduced mobility.
Current treatments often focus on painkillers or, in severe cases, joint replacement surgery. But for many people, medications don’t work well or cause side effects, and surgery may feel like too big a step.
In Europe, especially in countries like Germany and Spain, low-dose radiation has been used for decades to help relieve joint pain. But in many other countries, there is little awareness of this option, and high-quality studies comparing it to placebo treatments have been lacking—until now.
This Korean trial enrolled 114 patients with mild to moderate knee osteoarthritis across three academic centers.
Participants were randomly assigned to one of three groups: a group receiving a low dose of radiation (3 Gy), a group receiving a much lower dose (0.3 Gy), or a placebo group who underwent a sham procedure where the setup looked like real radiation therapy but no radiation was given.
Everyone received six sessions of treatment and did not know which group they were in. To keep results clear, only acetaminophen was allowed for pain relief during the four-month follow-up.
After four months, the results were striking. Seventy percent of patients in the 3 Gy group achieved meaningful improvement in pain and function, compared to 42% in the placebo group. People in the 0.3 Gy group did not show a significant difference from placebo.
In other words, the low dose of 3 Gy worked better than placebo, while the very low dose did not. Improvements were also seen in composite scores of pain, stiffness, and physical function—56.8% of the 3 Gy group reported better outcomes compared to 30.6% of the placebo group. Importantly, no treatment-related side effects were observed.
The researchers say this trial is different from past studies because it carefully controlled pain medication use and included a placebo group. These steps helped them show that the benefits were truly from the radiation itself, not from other factors like pain relievers or patient expectations.
Interestingly, about 40% of people in the placebo group still reported meaningful improvement—something that is common in osteoarthritis research and highlights the strong placebo effect in this condition.
Low-dose radiation is not a cure for osteoarthritis. It does not rebuild cartilage or fix severely damaged joints. However, for people with mild to moderate disease, it could delay the need for joint replacement and offer a middle-ground option between pain medication and surgery.
Because the doses used are a tiny fraction of what is used to treat cancer and are directed at joints far from vital organs, the risk of side effects appears low.
Experts emphasize that this treatment should be considered as part of shared decision-making alongside other standard approaches like weight loss, physical therapy, and medications.
Ongoing studies are looking at how long the benefits last and how low-dose radiation compares to other treatments like injections. Larger trials will also examine whether certain subgroups of patients benefit more than others.
This research suggests low-dose radiation could be a valuable addition to the options available for people with knee osteoarthritis, especially when drugs and injections fail. But longer-term results and larger studies are needed before it becomes widely adopted outside Europe.
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