A minimally invasive procedure targeting abnormal blood vessels in the knee could provide lasting relief for people with osteoarthritis, offering a potential alternative to joint replacement.
In a study of 194 patients, researchers found that treatment using tiny particles that dissolve within hours was associated with a substantial reduction in knee pain and improved mobility. Benefits persisted for at least 12 months, with 80% of patients assessed at 1-year follow-up reporting clinically significant pain relief.
The approach, known as genicular artery embolization, aims to interrupt the inflammation and abnormal growth of blood vessels that contribute to chronic knee pain. Rather than replacing the damaged joint, doctors use a thin catheter to deliver microscopic particles directly into specific blood vessels.
The results, published in the journal Radiologysuggest that this technique could provide another option for patients who have exhausted conventional treatments but are unable or unwilling to undergo knee replacement surgery.
Why knee arthritis is so difficult to treat
Osteoarthritis is the most common form of arthritis worldwide and a major cause of disability. According to the World Health Organization, knee osteoarthritis affects more than 365 million adults worldwide.
The disease develops as cartilage, the protective tissue that cushions the ends of bones, gradually deteriorates. But osteoarthritis is not limited to cartilage damage. Inflammation within the joint, changes in surrounding tissues, and increased sensitivity of pain-signaling nerves can all contribute to persistent discomfort.
For many people, the consequences go far beyond occasional knee pain. Daily activities such as walking, climbing stairs, exercising, or standing for long periods of time may become increasingly difficult.
Treatments usually begin with physical therapy, medications, and injections into the affected joint. When these approaches no longer provide adequate relief, knee replacement surgery may eventually be considered. However, surgery is not appropriate or desirable for everyone.
“For many patients with knee osteoarthritis, there is a real treatment gap today,” said Florian Nima Fleckenstein, MD, deputy director of the Interventional Radiology Campus Mitte, Charité – Universitätsmedizin Berlin. “Conservative measures such as intra-articular injections no longer provide sufficient relief, but joint replacement is not an option for medical or personal reasons.”
A different way to combat knee arthritis pain
The treatment being studied, genicular artery embolization (GAE), approaches knee arthritis in an unusual direction. Instead of focusing directly on damaged cartilage, it targets abnormal blood vessels that develop around an inflamed joint.
These vessels can form in and around the synovium, a thin membrane lining the inside of the joint. As the vessels multiply, they can contribute to inflammation and promote the growth of sensory nerves involved in pain transmission.
GAE is designed to interrupt this process by reducing blood flow through abnormal vessels while preserving normal circulation to the knee.
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 aim of reducing inflammation and pain.
This technique is called superselective embolization because doctors target specific small arteries rather than blocking circulation throughout the entire joint. It does not require an open surgical incision or knee replacement.
Researchers have previously studied both temporary blocking agents and permanent microscopic particles. Each approach has potential drawbacks, including differences in how precisely particles can be delivered and how long they stay inside blood vessels.
For this study, the team looked at rapidly absorbable gelatin-based microspheres. These precisely sized spherical particles are designed to dissolve within hours, potentially combining the benefits of temporary agents with the controlled delivery of permanent microspheres.
“GAE is a completely new treatment regimen that targets abnormal hypervascularity around the joint and, in turn, modulates the pathological neurovascular environment,” said Dr. Fleckenstein.
Hypervascularity refers to an unusually high concentration of blood vessels. The pathological neurovascular environment describes the abnormal interactions between these vessels and the pain-signaling nerves in the affected tissue.
“By reducing both inflammation and pain, GAE with resorbable microspheres could be the first procedure to modify the course of the disease, thereby slowing its progression.”
The question of whether this procedure can actually slow the progression of osteoarthritis remains open. Although reducing inflammation could theoretically influence the disease, the study did not demonstrate that GAE prevents cartilage deterioration or reverses existing joint damage.
Nearly 200 patients have undergone the procedure
To evaluate this approach, researchers conducted a prospective, single-center study involving 194 patients suffering from osteoarthritis-related knee pain. Participants included 114 women and 80 men, with a median age of 69 years 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 knee injections.
“We think these results have real weight because they come from real data,” Dr. Fleckenstein said. “With this large and inclusive study design, our participants are the exact patients that doctors encounter every day in their offices. »
The interventions took place between July and November 2024. Forty-five participants (23%) suffered from osteoarthritis affecting both knees and received two separate treatments, with the second carried out within four weeks of the first.
In total, researchers performed 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 affected blood vessels were successfully treated.
The safety results were also encouraging. No moderate or serious adverse events were recorded and mild and temporary complications occurred in 6.7% of procedures.
These included brief discoloration of the skin near the treated area and a superficial collection of blood near the catheter insertion site. Everything was resolved without lasting complications.
Knee arthritis pain decreased and remained lower for a year
Researchers monitored pain, movement and quality of life before treatment and at several intervals afterward. Assessments were carried out at six weeks, three months, six months and 12 months. An orthopedic surgeon also examined the patients in person 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 result was the lasting reduction in knee pain.
Using the Numerical Rating Scale (a 0 to 10 measure of pain intensity), median pain scores increased from 7 before treatment to 4 after six weeks. After six months, the median score had fallen to 3 and remained at this level at 12-month follow-up.
This represents a reduction of more than half compared to the initial median pain score, with benefits still visible one year after treatment.
“In our cohort, we saw a significant decline in pain and a significant increase in function, including sports, hobbies and daily activities,” Dr. Fleckenstein said. “More importantly, their quality of life has improved significantly.”
Patients also reported improved mobility and quality of life
The improvements go beyond pain reduction. Researchers used the Knee Injury and Osteoarthritis Outcome Score, a standardized questionnaire that assesses the impact of knee problems on symptoms, mobility, leisure activities and daily life.
In all five areas assessed, patients reported significant progress over 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 increased from 15 to 36, indicating improvements in more physically demanding activities.
Scores measuring osteoarthritis symptoms increased from 51 to 68, while the pain category improved from 44 to 65 (where 0 indicates extreme knee pain and 100 indicates no pain).
Quality of life scores also increased significantly, from 19 before treatment to 40 after 12 months.
To determine whether these changes were large enough to be important to patients, researchers applied established thresholds for clinically meaningful improvement.
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 significant improvements.
These thresholds are known as the minimum clinically important difference. Simply put, they distinguish changes that may be noticeable in everyday life from smaller statistical differences that may have little practical significance.
At 12 months, 80% of participants who completed the pain assessment exceeded the threshold for clinically significant improvement.
“Our study demonstrates that GAE using rapidly absorbable gelatin-based microspheres is a safe, minimally invasive therapy that provides significant pain relief and functional improvement in participants with osteoarthritis-related knee symptoms for at least 12 months,” said Dr. Fleckenstein. “By embolizing the pathological…
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