Relief from osteoarthritis pain with low-dose radiation therapy

Before Barbara Coates met radiation oncologist John Plastaras, MD, PhD, it was impossible for her to walk without excruciating pain. Within 24 hours of her first treatment session with him, she was moving better than she had in years and crying tears of joy.

The 58-year-old Montgomery County resident had severe osteoarthritis, a condition where the cartilage that cushions the ends of your bones wears down over time. Without enough cartilage, bones rub against each other, causing pain, stiffness, and swelling—for some patients, with every step.

Coates was one of the first patients at Penn Medicine to receive low-dose radiation therapy to treat her osteoarthritis. While radiation therapy is most often used for cancer treatment, it’s gaining traction as a tool for other non-cancerous conditions, and Penn Medicine physicians are leading the charge for implementing low-dose radiation therapy in a patient-centric fashion while advancing research on these approaches.

“I’d been in crippling pain for at least five years,” Coates recalled. Her osteoarthritis was exacerbated by two other conditions called Ehlers-Danlos syndrome (EDS) and mast cell disease. EDS is an inherited condition that results in overly flexible joints and fragile skin, while mast cell disease causes sensitivity to drugs and allergens in the environment.

The EDS meant that she needed to exercise daily—no matter how painful it was—to strengthen the muscles holding her joints together. The mast cell disease meant that she wasn’t a good candidate for injections or surgery, the typical treatments for osteoarthritis.

As a former Division-1 athlete and USA Field Hockey Junior National Team coach, who spent time managing a physical therapy clinic and working in academic medicine administration, Coates was well prepared to face the physical challenges of her ailments head on: “I have the attitude of an athlete: let’s keep going,’” she said.

So, when her Physical Medicine and Rehabilitation physician in Elkins Park told her that his brother, a radiation oncologist at Penn Medicine, was piloting a new treatment, Coates was all in to try it.

‘Life-altering’ pain relief

Using low-dose radiation therapy for arthritis isn’t new, per se. The approach has been widely used in Europe for decades but didn’t gain traction in the U.S. until recently.

“German studies have shown as much as a 70 percent reduction in arthritis pain with low-dose radiation treatment,” said Plastaras, who is the chief of Radiation Oncology and Proton Therapy at Penn Presbyterian Medical Center. A placebo-controlled clinical trial performed in Korea and presented at the 2025 American Society for Radiation Oncology (ASTRO) Annual Meeting found that low-dose radiation therapy provided substantial relief to people with painful knee osteoarthritis.

While treating cancer requires enough radiation exposure to destroy tumor cells and can come with significant side effects, “low-dose” radiation to treat arthritic joints is less than five percent of the amounts typically used for cancer treatments. At these levels, side effects are uncommon.

Precisely targeting the affected joints with low doses of radiation, spread over six sessions, helps minimize inflammation in the joint, alleviating pain.

“I did all six sessions, but felt immediate relief after the first one,” Coates said. “When I got home, I had to get something out of the basement, and I flew up the stairs like there was nothing wrong with me. By the second treatment, I was able to sit cross-legged. I was doing things that had been impossible before, with no pain. It’s been life-altering.”

Radiation for a high-risk heart condition

Arthritis isn’t the only non-cancer condition Penn Medicine physicians are treating with low-dose radiation therapy. Keith Cengel, MD, PhD, has also been testing the approach for certain cases of ventricular tachycardia (VT), a potentially life-threatening irregularly fast heartbeat, in individuals for whom traditional treatment approaches have already been tried without success.

“We’re aiming at the faulty electrical circuit in the heart and trying to interrupt it with radiation,” explained Cengel, who is the Penn lead for a multisite, randomized clinical trial that’s comparing the approach to traditional ablation and assessing rates of VT, as well as side effects and quality of life. “Our goal is to figure out where radiation fits in the toolkit for treating these patients.”

Cengel added that the dose that doctors are using for VT is similar to what’s used for lung cancer.

Expanding radiation capacity for cancer and osteoarthritis

So far, Plastaras and his team have treated more than 150 patients with osteoarthritis, and in January 2026, a dedicated clinic is opening at Penn Presbyterian Medical Center, where the health system is currently expanding its radiation therapy capabilities and building a fourth proton therapy location. The low-dose radiation treatment is designed for arthritis in joints that are not part of the spine, like the ankle, knee, or wrist. It’s limited to patients who are not yet candidates for joint replacement surgery, or who have had persistent pain or dysfunction despite trying other therapies.

“Since this treatment is relatively new to the U.S., we’re going to study it in a clinical research protocol, meaning we’ll track the treatments and outcomes, so we can report on what works and what doesn’t,” Plastaras said.

Over the next six months, the team hopes to treat over 100 patients while another medical linear accelerator (LINAC) machine is added to Penn Presbyterian to increase capacity for both cancer and non-cancer patients.

“While our priority as radiation medicine physicians will always be ensuring we can meet the needs of patients facing life-threating cancer diagnoses, it’s exciting to extend our skill set to another patient population,” Plastaras said. “Low-dose radiation therapy offers a minimally invasive treatment option that has the potential to dramatically improve quality of life for many adults hampered by osteoarthritis joint pain and dysfunction.”