A promising new treatment for knee arthritis may provide lasting relief for people struggling with osteoarthritis, and offer a potential alternative to joint replacement surgery by using tiny, dissolvable particles to block abnormal blood vessels and ease inflammation and pain, suggest scientists in Berlin.
In a study of 194 patients – the findings were published in Radiology – 80% experienced clinically meaningful pain relief lasting at least 12 months.
The approach, known as genicular artery embolisation (GAE), aims to interrupt the inflammation and abnormal blood vessel growth that contribute to chronic knee pain. Rather than replacing the damaged joint, doctors use a thin catheter to deliver the microscopic particles directly into specific blood vessels.
The researchers suggest this technique could provide another option for patients who have exhausted conventional treatments but cannot or do not want to undergo knee replacement surgery.
Why knee arthritis is so difficult to treat
Osteoarthritis is the world’s most common form of arthritis and a major cause of disability, affecting more than 365m adults worldwide.
The condition develops as cartilage, the protective tissue that cushions the ends of bones, gradually deteriorates. But osteoarthritis involves more than cartilage damage.
Inflammation within the joint, changes in surrounding tissues, and increased sensitivity of pain signalling nerves can all contribute to persistent discomfort.
Treatments typically begin with physical therapy, medication, and injections into the affected joint. When these approaches stop providing adequate relief, knee replacement surgery may eventually be considered, but this is not appropriate or desirable for everyone.
“For many patients with knee osteoarthritis, there is a real treatment gap,” said Florian Nima Fleckenstein, MD, deputy head of Interventional Radiology Campus Mitte, Charité–Universitätsmedizin Berlin. “Conservative measures like intra-articular injections no longer provide sufficient relief, but joint replacement is not always an option for medical or personal reasons.”
The treatment being investigated, GAE, approaches knee arthritis from an unusual direction. Instead of focusing directly on damaged cartilage, it targets the abnormal blood vessels that develop around an inflamed joint.
These vessels can form within and around the synovium, a thin membrane lining the inside of the joint. As the vessels multiply, they can contribute to inflammation and encourage the growth of sensory nerves involved in transmitting pain.
GAE is designed to interrupt this process by reducing blood flow through the abnormal vessels while preserving the knee’s normal circulation.
During the procedure, an interventional radiologist inserts a thin catheter into an artery and carefully guides it toward the affected blood vessels. Tiny particles are then injected to block selected vessels, with the goal of reducing inflammation and pain.
The technique is called superselective embolisation because doctors target specific small arteries rather than blocking circulation throughout the joint. It does not require an open surgical incision or replacement of the knee.
Researchers have previously investigated both temporary blocking agents and permanent microscopic particles. Each has potential drawbacks, including differences in how precisely the particles can be delivered and how long they remain inside the blood vessels.
For this study, the team examined rapidly resorbable, gelatin-based microspheres: precisely sized, spherical particles engineered to dissolve within hours, potentially combining the advantages of temporary agents with the controlled delivery of permanent microspheres.
“AE is a whole new treatment regimen that targets abnormal hypervascularity around the joint and, in turn, modulates the pathological neurovascular environment,” said Fleckenstein.
Hypervascularity refers to an unusually high concentration of blood vessels. The pathological neurovascular environment describes the abnormal interactions between those vessels and pain signalling nerves in the affected tissue.
Whether the procedure can actually slow osteoarthritis progression remains an open question. Although reducing inflammation could theoretically influence the disease, the study did not demonstrate that GAE prevents cartilage deterioration or reverses existing joint damage.
Single-centre study
To evaluate the approach, researchers conducted a prospective single-centre study involving 194 patients with osteoarthritis-related knee pain: 114 women and 80 men, with a median age of 69 and a median body mass index of 28.4.
All had continued to experience symptoms despite at least three months of conventional care, including physical therapy, anti-inflammatory medications, and injections into the knee.
The procedures took place between July and November 2024: 45 participants had osteoarthritis affecting both knees and received two separate treatments, with the second performed within four weeks of the first.
Altogether, the researchers carried out 239 GAE procedures.
Doctors used real-time X-ray imaging, known as fluoroscopy, to guide the catheter and deliver the particles to the targeted arteries. All 239 procedures were technically successful, meaning the intended blood vessels were successfully treated.
The safety findings were also encouraging. No moderate or severe adverse events were recorded, and mild, temporary complications occurred in 6.7% of procedures.
These included brief skin discolouration near the treated area and one superficial collection of blood near the catheter insertion site. All resolved without lasting complications.
Pain levels dropped for a year
The researchers monitored pain, movement, and quality of life before treatment and at several intervals afterward. Assessments were conducted at six weeks, three months, six months, and 12 months. An orthopaedic surgeon also examined patients at the six-month follow-up.
Participant retention remained relatively high throughout the study. Follow-up rates were 94% at six weeks (183/194), 89% at three months (172/194), 89% at six months (171/194), and 79% at 12 months (154/194).
The most striking finding was the sustained reduction in knee pain.
Using the Numeric Rating Scale (a 0-to-10 measure of pain intensity), median pain scores fell from 7 before treatment to 4 after six weeks. By six months, the median score had declined to 3, and it remained at that level at the 12-month follow-up, a reduction of more than half from the original median pain score, with benefits still apparent a full year after treatment.
“We saw a significant drop in pain and an increase in function, including sports and recreation and daily activity,” Fleckenstein said. “Most importantly, their quality of life significantly increased.”
Researchers used the Knee Injury and Osteoarthritis Outcome Score to evaluate how knee problems affect symptoms, mobility, recreation, and everyday life.
Across all five areas assessed, patients reported meaningful progress during the year following treatment.
Median scores for daily activities increased from 53 to 71.5, suggesting that routine movements such as walking and climbing stairs became easier. Sports and recreation scores climbed from 15 to 36. Scores measuring osteoarthritis symptoms rose from 51 to 68, while the pain category improved from 44 to 65 (where 0 indicates extreme knee pain and 100 indicates no pain at all).
Previous studies have identified a reduction of at least 2.0 points on the Numeric Rating Scale and an increase of at least 10 points in the Knee Injury and Osteoarthritis Outcome Score categories as meaningful improvements.
These thresholds are known as the minimum clinically important difference. In simple terms, they distinguish changes that are likely to be noticeable in daily life from smaller statistical differences that may have little practical significance.
At 12 months, 80% of participants who completed the pain assessment exceeded the clinically meaningful improvement threshold.
What other studies reveal about knee artery embolisation
The results add to a growing body of evidence investigating whether blocking abnormal knee blood vessels can offer sustained relief from osteoarthritis.
A randomised study published in Clinical Radiology in 2026 provided encouraging findings. Researchers compared GAE combined with standard care against standard care alone in 50 patients. After one year, pain scores had improved by 72.7% in the embolisation group, compared with 24.2% in the standard care group. The treated patients also reported better knee function.
However, that study used polyvinyl alcohol particles rather than the dissolving gelatin particles examined by Fleckenstein’s team. It also did not include a sham procedure, making it difficult to separate the treatment’s physical effects from patients’ expectations.
Other research has raised important questions about how much of the improvement is caused by embolisation itself.
A randomised, sham-controlled study published in European Radiology in April 2026 followed 58 patients for 12 months. Both the GAE and sham treatment groups experienced sustained reductions in pain, but researchers found no statistically significant difference between them. MRI examinations also failed to identify a significant reduction in joint inflammation attributable to embolisation.
Similarly, an analysis appearing in the September 2026 issue of the European Journal of Radiology examined 22 studies involving 633 patients. Although pain scores often improved substantially after treatment, the researchers found no statistically significant advantage over sham procedures when results from three randomised trials were combined.
A separate June 2026 analysis of 45 studies involving 2 205 patients also documented improvements in pain and function, but judged the overall certainty of the evidence to be low or very low.
Combined, these findings suggest that GAE is associated with promising improvements, particularly in observational studies, but more rigorous trials are needed to establish how much benefit comes directly from blocking the blood vessels.
Despite the remaining uncertainties, researchers and medical specialists are increasingly exploring GAE as a possible option for patients who have limited alternatives.
In a 2026 position statement, the Society of Interventional Radiology supported offering the procedure to appropriately selected patients whose symptoms persist despite conservative treatment, particularly those who cannot undergo or wish to delay knee replacement surgery.
The study led by Fleckenstein provides particularly valuable information about rapidly resorbable gelatin microspheres. With nearly 200 participants, it represented the largest published clinical investigation of this specific approach at the time.
Still, because the study did not include an untreated or sham treatment comparison group, it cannot establish how much of the observed improvement resulted directly from the procedure. The researchers also did not evaluate whether the treatment slows cartilage loss or prevents patients from eventually needing joint replacement.
Longer follow-up and larger controlled trials will be essential to determine how durable the benefits are, which patients respond best, and whether dissolving particles offer advantages over other embolisation materials.
For patients whose knee arthritis continues to interfere with everyday life despite medication, therapy, and injections, the approach nevertheless represents an increasingly studied possibility.
Study details
Genicular Artery Embolisation Using Rapidly Resorbable Gelatin-based Microspheres for Osteoarthritis-related Knee Pain
Florian Nima Fleckenstein, Dina David, Paolo Garducci et al.
Published in Radiology on 16 June 2026
Abstract
Background
Genicular artery embolisation (GAE) is an emerging minimally invasive therapy for osteoarthritis (OA)–related knee pain. Traditional embolic agents such as imipenem-cilastatin and permanent microspheres have distinct limitations. Rapidly resorbable gelatin-based microspheres (RRGMs), designed specifically for GAE, may offer a promising alternative.
Purpose
To evaluate the safety and clinical outcomes of GAE using RRGMs in participants with OA-related knee pain.
Materials and Methods
This prospective, single-centre observational study included consecutive participants with OA-related knee pain refractory to conservative treatment who underwent GAE using RRGMs between July and November 2024. Safety, the numeric rating scale (NRS) score (range, 0–10), and the Knee Injury and Osteoarthritis Outcome Score (KOOS) (range, 0–100) were assessed at 6 weeks and 3, 6, and 12 months after treatment. Clinical benefits were evaluated using the minimum clinically important difference (MCID). Descriptive statistics were used, and changes over time were assessed with the Friedman nonparametric repeated-measures test.
Results
A total of 194 participants (median age, 69 years; IQR, 60.5–75 years; 114 female) underwent 239 GAE procedures using RRGMs. The follow-up rates were 94% at 6 weeks (183 of 194 participants), 89% at 3 months (172 of 194 participants), 89% at 6 months (171 of 194 participants), and 79% at 12 months (154 of 194 participants). All the procedures (239 of 239) were technically successful. Transient skin discolouration occurred after 15 procedures (6.3%), and one participant developed a superficial groin hematoma (0.4%), all of which resolved without sequelae. No moderate or severe adverse events were observed. The median NRS pain score decreased from 7 (IQR, 6–8) at baseline to 3 (IQR, 2–5) at 12 months (P < .001), corresponding to a median reduction of 4 points (95% CI: 3.5, 4.0). At 12 months, 55%–80% of participants achieved improvements exceeding the MCID across all KOOS subscores.
Conclusion
GAE using RRGMs is safe and is associated with clinically meaningful improvement in participants with OA-related knee pain.
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