Resorbable microspheres tied to lasting knee OA pain relief

Clinical takeaway: For knee OA refractory to injections and physical therapy, genicular artery embolization with a resorbable agent may eventually offer a durable, low-risk option short of joint replacement.

For knee OA that no longer responds to conservative care, the options thin out fast. Genicular artery embolization (GAE) offers a minimally invasive path, blocking the abnormal periarticular vessels thought to drive inflammation and pain.

Existing GAE agents force a trade-off: a widely used off-label antibiotic crystal lacks calibrated particle size, while permanent microspheres raise concerns about long-term vascular effects. The dissolvable gelatin-based agent tested here, Nexsphere-F, was designed to offer a middle ground with more consistent structure alongside resorbability.

Researchers tracked pain, function, and safety in 194 patients over a year in the single-arm study. Median pain on the numeric rating scale (NRS; range 0-10) dropped to 3 at 12 months from 7 at baseline, a median 4-point reduction, and the improvement held across the full year. At 12 months, 80% of participants cleared the minimum clinically important difference on pain, defined as a drop of at least 2 points.

Function and quality of life improved across the board: daily activity rose to 71.5 from 53, sports and recreation to 36 from 15, and quality of life to 40 from 19. This is on the Knee Injury and Osteoarthritis Outcome Score (KOOS) scales, which span 0 to 100 with higher numbers indicating better performance. Across the five KOOS subscores, the share of participants meeting the clinically important threshold ranged from 55% to 69%, depending on the domain.

In this prospective single-center study, 194 adults with conservative-care-refractory knee OA (median age 69; 114 women; median BMI 28.4) underwent 239 GAE procedures with the resorbable agent between July and November 2024. Roughly a quarter had bilateral treatment. Mild, self-limiting events followed 6.7% of procedures, with no moderate or severe events. Follow-up ran to 12 months, with 79% retained at the final visit.

The results extend the procedure's safety record to a resorbable agent and suggest the benefit holds for a full year, but the single-arm design is a limitation. A randomized, controlled trial is the next test before the agent earns a defined place in the pathway.

Nexsphere-F is cleared for use in Europe, Canada, and South Korea but remains investigational in the US. Here it carries Breakthrough Device Designation, and enrollment began in October 2025 in RESORB, an FDA pivotal trial randomizing patients to GAE with the agent or corticosteroid injection.

"GAE with resorbable microspheres may be the first procedure that alters the course of the disease, slowing its progression," said Florian Nima Fleckenstein, MD, deputy head of interventional radiology at Charité Universitätsmedizin Berlin.

Source: Fleckenstein FN. Radiology. 2026 Jun 16. Genicular Artery Embolization Using Rapidly Resorbable Gelatin-based Microspheres for Osteoarthritis-related Knee Pain