Radiation Eases Knee Arthritis Pain

For millions of people suffering from knee osteoarthritis, the path forward often seems to lead to one of two undesirable destinations: a lifetime of pain medications or invasive joint replacement surgery. But a recent clinical trial may have uncovered a promising middle ground that’s both non-invasive and drug-free—low-dose radiation therapy. This treatment, typically associated with cancer care, has shown significant potential in relieving the pain and improving the function of arthritic knees.

The Clinical Trial: How Low-Dose Radiation Eases Knee Pain

The research, led by a team from Seoul National University College of Medicine and the SMG-SNU Boramae Medical Center, was presented at the 2025 Annual Meeting of the American Society for Radiation Oncology (ASTRO)—a prestigious gathering of over 10,000 radiation oncology professionals. This immediately lends scientific credibility to the findings.

The clinical trial involved 114 participants with primary knee osteoarthritis, all experiencing moderate joint damage visible on X-rays and significant pain while walking. These participants were divided into three groups:

A very low-dose radiation group (0.3 Gy total, administered in six sessions of 0.05 Gy each)
A low-dose radiation group (3 Gy total, administered in six sessions of 0.5 Gy each)
A sham treatment group that did not receive actual radiation

To put these doses in perspective, a single chest X-ray delivers about 0.1 mGy of radiation, while a chest CT scan delivers approximately 6-7 mGy. Each treatment session in this study delivered 500 mGy (0.5 Gy), which sounds like a lot, but is still considered low-dose compared to cancer radiation therapy, which typically involves total doses of 50-70 Gy.

The results were compelling. After four months, about 70% of patients in the 3 Gy group showed significant improvement compared to only 42% in the sham group. Even more impressively, over half (57%) of the 3 Gy group experienced a clinically meaningful improvement in joint pain and function scores, compared to just 31% in the sham group. The very low-dose group (0.3 Gy) showed improvement in 58% of participants, but this was not significantly different from the sham group, suggesting their results might be due to chance.

Safety and Side Effects

Importantly, the treatment was deemed safe, with no reported side effects or toxicity. According to Dr. Byoung Hyuck Kim, the trial’s principal investigator, “There’s a misconception that medicinal, or therapeutic, radiation is always delivered in high doses. But for osteoarthritis, the doses are only a small fraction of what we use for cancer, and the treatment targets joints that are positioned away from vital organs, which lowers the likelihood of side effects.”

Understanding Osteoarthritis and Its Burden

To appreciate the significance of this new treatment option, it’s important to understand the scale of the osteoarthritis problem. According to the Centers for Disease Control and Prevention, about 33 million U.S. adults have osteoarthritis (OA), making it one of the most common forms of arthritis. Knee osteoarthritis specifically affects approximately 10% of men and 13% of women aged 60 and older, with prevalence increasing as the population ages.

Osteoarthritis occurs when the protective cartilage that cushions the ends of bones wears down over time. In the knee, this leads to pain, stiffness, swelling, and reduced mobility. For many patients, especially those with advanced disease, the only definitive solution has traditionally been knee replacement surgery.

Current Non-Surgical Treatment Options

Before considering surgery, patients typically try a range of non-surgical treatments with varying degrees of success:

Non-steroidal anti-inflammatory drugs (NSAIDs) like naproxen, which research suggests is the most effective individual treatment for improving both pain and function
Corticosteroid injections for short-term pain relief
Physical therapy and exercise programs
Weight loss and lifestyle modifications
Bracing for joint support

However, these treatments often provide only temporary relief and can come with significant side effects, particularly with long-term use of NSAIDs or repeated steroid injections. This creates a therapeutic gap that low-dose radiation therapy might help fill.

The Science Behind Low-Dose Radiation Therapy for OA

While the exact mechanism of action is still being researched, low-dose radiation therapy appears to work primarily through anti-inflammatory effects. Rather than destroying tissue like high-dose radiation used in cancer treatment, these low doses seem to reduce inflammation in the joint tissues, which is a key driver of osteoarthritis pain and dysfunction.

Low-dose radiation therapy for benign conditions like osteoarthritis has been used in European countries for decades, with studies suggesting moderate to long-term pain relief and improvement in mobility. According to research published in the International Journal of Radiation Oncology, Biology, Physics, numerous studies outside the US have shown the benefits of LDRT for joints affected by OA.

Limitations and Future Research

The researchers caution that this treatment may not be as effective for people with severe osteoarthritis where the joint structure is already significantly damaged. “For severe osteoarthritis, where the joint is physically destroyed and cartilage is already gone, radiation will not regenerate tissue,” explains Dr. Kim.

The team is currently conducting a 12-month follow-up assessment to better understand the longevity of benefits, and they plan to conduct larger trials to evaluate the treatment’s effectiveness in specific population groups and compare it directly with injections and medication regimens.

Implications for Patient Care

If these findings are confirmed in larger trials, low-dose radiation therapy could represent a significant advancement in osteoarthritis care. It offers a non-pharmacological, non-invasive option that could delay or even prevent the need for knee replacement surgery in many patients. This would not only improve quality of life for patients but could also reduce healthcare costs associated with surgical interventions and long-term medication use.

This treatment approach addresses a key challenge in osteoarthritis management: finding safe, effective moderate interventions between weak pain medications and aggressive surgery. For patients who don’t respond well to traditional treatments or experience significant side effects, low-dose radiation therapy could provide a welcome alternative.

As with any new medical treatment, further research is needed to fully understand the long-term safety profile, optimal dosing regimens, and patient selection criteria. However, this clinical trial represents an exciting step forward in the search for better treatments for one of the most common and disabling conditions affecting older adults.