Novel embolization technique reduces pain from knee osteoarthritis

Embolization of abnormal blood vessels using rapidly resorbable gelatin-based microspheres is safe and provides significant, lasting pain relief and functional improvement for patients with osteoarthritis-related knee pain, according to a new study published today in Radiology, a journal of the Radiological Society of North America (RSNA).

Osteoarthritis is the most common form of arthritis. It causes inflammation, stiffness, reduced mobility and sensory nerve pain. According to the World Health Organization, knee osteoarthritis affects over 365 million adults worldwide and is one of the leading contributors to disability.

For many patients with knee osteoarthritis, there is a real treatment gap today. Conservative measures such as intra-articular injections no longer provide sufficient relief, but joint replacement is not an option for medical or personal reasons."

Florian Nima Fleckenstein, M.D., deputy head of Interventional Radiology Campus Mitte, Charité - Universitätsmedizin Berlin

Genicular artery embolization (GAE) is an emerging minimally invasive treatment that targets abnormal blood vessels using superselective embolization. In an osteoarthritic knee, these abnormal vessels build up around the joint and drive inflammation and pain. During GAE, an interventional radiologist guides a thin catheter directly to each affected vessel and injects tiny particles to block it, calming the inflammation and easing the pain without surgery.

For the study, researchers hypothesized that GAE using rapidly resorbable, gelatin-based microspheres could integrate the favorable characteristics of temporary embolic agents and permanent microspheres while eliminating their limitations. Rapidly resorbable, gelatin-based microspheres are size-calibrated, spherical particles designed to dissolve within hours.

"GAE is a whole new treatment regimen that targets abnormal hypervascularity around the joint and, in turn, modulates the pathological neurovascular environment," Dr. Fleckenstein said. "By reducing both inflammation and pain, GAE with resorbable microspheres may be the first procedure that alters the course of the disease, slowing its progression."

The prospective single-center study included 114 women and 80 men with osteoarthritis-related knee pain who did not respond to at least three months of conservative treatment, including physiotherapy, anti-inflammatory drugs and intra-articular injections. The median age of the 194 participants was 69 years, and median body mass index was 28.4.

"We believe these results carry real weight because they come from real-world data," Dr. Fleckenstein said. "With this broad, inclusive study design, our participants are exactly the patients that physicians encounter every day in their practices."

All participants underwent GAE with the resorbable microspheres between July and November 2024. Forty-five participants (23%) underwent two GAE procedures for bilateral knee osteoarthritis, with the second GAE conducted within four weeks of the first procedure.

In total, the patients underwent 239 GAE procedures using the resorbable microspheres. Embolization was performed under image (fluoroscopic) guidance. All procedures were technically successful with no moderate or severe adverse events and only mild, self-limited reactions in 6.7% of the study group.

Outcomes were analyzed at the participant level at baseline, six weeks, and three, six and 12 months following the procedure. The six-month assessment was performed in person by an orthopedic surgeon. Follow-up rates in the study were 94% of the patients at six weeks (183/194), 89% at three months (172/194), 89% at six months (171/194) and 79% at 12 months (154/194).

"In our cohort, we saw a significant drop in pain and a significant increase in function, including sports and recreation and daily activity," Dr. Fleckenstein said. "Most importantly, their quality of life significantly increased."

Median pain scores fell quickly and kept improving. On the Numeric Rating Scale (a 0-to-10 measure of pain intensity), scores dropped from 7 at baseline to 4 at six weeks and to 3 at the 6-, and 12-month follow-ups - a sustained reduction maintained throughout the year.

From baseline to the 12-month follow-up, Knee Injury and Osteoarthritis Outcome Score sub-scores improved across all domains: increased median daily activity scores increased from 53 to 71.5, sports and recreation increased from 15 to 36. Osteoarthritis-related symptoms improved from 51 to 68, pain scores improved from 44 to 65 (where 0 indicates extreme knee pain and 100 indicates no pain at all), and quality of life increased from 19 to 40.

Based on prior studies, a reduction in a Numeric Rating Scale pain score of ≥ 2.0 points and a change of ≥ 10 points in the Knee Injury and Osteoarthritis Outcome Score sub-scores are considered clinically meaningful and are defined as a minimum clinically important difference.

At the 12-month follow-up, 80% of study participants achieved improvements exceeding the minimum clinically important difference, based on the Numeric Rating Scale scores.

"Our study demonstrates that GAE using rapidly resorbable gelatin-based microspheres is a safe, minimally invasive therapy that provides meaningful pain relief and functional improvement in participants with osteoarthritis-related knee symptoms for at least 12 months," Dr. Fleckenstein said. "By embolizing the pathological vessels, we're able to normalize the vessel structure - and, in turn, the neuronal structure of the knee."

Dr. Fleckenstein noted that with almost 200 patients, this is the largest body of evidence yet for GAE using rapidly resorbable microspheres.

"This lets us speak about safety and efficacy with real confidence," he said. "For the right patient, it can mean lasting relief from a single, minimally invasive procedure - a meaningful new option between injections and joint replacement."

"Genicular Artery Embolization Using Rapidly Resorbable Gelatin-based Microspheres for Osteoarthritis-related Knee Pain." Collaborating with Dr. Fleckenstein were Dina David, M.S., Paolo Garducci, M.D., Tazio Maleitzke, M.D., Stephan Oehme, M.D., Lynn Jeanette Savic, M.D., Timo Alexander Auer, M.D., Bernhard Gebauer, M.D., Tobias Winkler, M.D., Ph.D., and Federico Collettini, M.D.