New knee procedure cuts arthritis pain in half for most patients

About 70% of patients who try a new outpatient procedure for knee osteoarthritis cut their pain scores in half or more, according to interventional radiologists at the University of Colorado Anschutz School of Medicine. The treatment blocks blood flow to inflamed tissue inside the joint rather than replacing it. Some patients report no pain at all afterward, and early follow-up data show relief lasting two to four years. For a disease that has long offered only medication or a full joint replacement, doctors there say the procedure fills a gap that has existed for decades.

Threading beads through the genicular arteries

Leigh Casadaban, an assistant professor of radiology and vascular interventional radiologist at the University of Colorado Anschutz School of Medicine, performs the procedure, called genicular artery embolization, by threading a catheter from a small incision in the leg crease through the femoral artery to the genicular arteries that feed the knee joint, guided by X-ray imaging. Once there, she releases tiny beads that block blood flow to the abnormal, inflamed vessels that grow into the joint lining as osteoarthritis worsens, cutting off a pathway that drives chronic pain signals. The procedure takes one to two hours under conscious sedation, and patients go home the same day rather than facing the weeks of rehabilitation that follow a joint replacement.

“[Doctors] find about 70% of patients have phenomenal results,” Casadaban, of the University of Colorado Anschutz School of Medicine, said. “They cut their pain scores in half, sometimes more. [The team has] a few patients with no pain at all after the procedure.” That figure, drawn from her clinic’s own patients and reported through the university’s research office, describes people who had exhausted conservative treatment but were not yet candidates, by choice or by medical judgment, for surgery. The mechanism behind it, blocking blood flow to inflamed tissue rather than repairing the joint itself, is why doctors describe it as treating the pain generator instead of the disease.

Filling the gap between pills and a full replacement

For years, physicians managing knee osteoarthritis have had two real paths: conservative care such as physical therapy, injections and anti-inflammatory drugs, or a total knee replacement once the joint has degraded enough to justify major surgery. Casadaban says genicular artery embolization targets the patients stuck between those extremes, people whose pain outlasts medication but who are reluctant to schedule a replacement, whether because of other health conditions, work obligations or simple hesitation about a joint surgery. “GAE is a promising minimally invasive procedure that may fill that spot,” she said, describing a category of patient her clinic previously had little to offer beyond more injections.

Cynthia Schraf-Fletcher, 74, is one of those patients. She had a total knee replacement on her left knee years earlier and chose embolization for her right knee about a year ago rather than a second operation. She described the result on the treated knee as “almost the same as the total knee replacement,” she said, but without the surgical incision, hospital stay or months of physical therapy that followed her earlier operation.

A regulatory push and an unsettled question of durability

Regulators have moved alongside the early clinical results. The Food and Drug Administration has granted breakthrough device status to several embolic products marketed for the procedure since 2021, including Merit Medical’s Embosphere Microspheres, a designation meant to speed federal review of technologies aimed at unmet medical needs. Casadaban’s team at CU Anschutz is separately running two clinical trials, one tracking joint fluid changes after treatment and another testing a temporary blocking device called Nexsphere-F, work aimed at answering questions the initial patient results cannot.

Peer-reviewed follow-up, including a two-year outcomes study published in the Journal of Vascular and Interventional Radiology, has tracked embolization patients well past the point where a placebo effect would typically fade. Separate case series out of Japan have followed responders for as long as four years, Casadaban said. The durability varies by patient, and the best-studied candidates so far have mild to moderate osteoarthritis rather than advanced, bone-on-bone joint damage, a distinction that will likely shape who insurers eventually cover for the procedure.

Not every patient responds. Roughly three in ten see little to no benefit, by Casadaban’s own accounting, and the procedure does not rebuild cartilage or reverse the structural damage osteoarthritis has already caused in the joint. It interrupts a pain pathway rather than repairing the underlying disease, which is also why Casadaban’s clinic screens candidates by imaging before scheduling anyone for treatment.

The clearest results so far have come from people with mild to moderate osteoarthritis rather than the advanced, bone-on-bone cases that typically prompt surgeons to recommend replacement outright. Patients whose X-rays already show extensive bone damage tend to see a smaller, shorter-lived response, according to Casadaban’s team, which is one reason the current trials are tracking imaging and joint-fluid markers alongside pain scores rather than relying on pain reports alone.

Whether embolization ultimately delays a knee replacement for years or only postpones an inevitable one is a question longer trials, including the ones now underway at CU Anschutz, are still built to answer. For now, Casadaban’s team is enrolling patients who fit the gap she describes: pain too severe for pills, but not yet ready for a scalpel.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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