What is GAE for knee arthritis?

Key facts

GAE is for knee arthritis pain that has not improved enough with treatments such as physical therapy, weight management, or injections².
It is done through a small catheter with numbing medicine and often light sedation. Most people go home the same day².
GAE targets inflamed tissue in the joint lining. It does not rebuild worn cartilage, and some people may still need a knee replacement later^1,2.
Evidence status as of October 2026: one small sham-controlled trial found less pain after GAE, and two larger ones found no clear difference from a sham procedure³.

How GAE works

Osteoarthritis wears away the cartilage that cushions the knee. It also causes ongoing inflammation². In many people, the joint lining (the synovium) becomes inflamed and grows extra small blood vessels. Researchers think these vessels, and the nerves that grow along with them, add to knee pain¹.

The small arteries around the knee are called the genicular arteries. In GAE, the doctor places tiny particles in the branches that feed the inflamed lining. The goal is to calm the inflammation and ease pain^1,2. Some doctors use particles that dissolve over time, and others use permanent ones. There is no agreed best choice yet¹.

Step 1. A small catheter is steered through the arteries to the small arteries around the knee, using X-ray pictures.
Step 2. Tiny particles go in through the catheter and slow blood flow to the extra small vessels in the inflamed lining.
Step 3. The catheter is removed. The goal is for the lining to become less inflamed, which may ease pain.

How genicular artery embolization works, in three steps, seen from the front of the knee. In knee osteoarthritis, the joint lining can become inflamed and grow extra small blood vessels. A simplified drawing, not to scale.

GAE does not rebuild cartilage or change the bones of the knee. It is a treatment for pain, not a cure for arthritis.

What GAE is like

Before. You meet the interventional radiologist to talk about your knee pain, the treatments you have tried, and your goals. Your team may ask for a recent standing knee X-ray and a knee MRI².

During. GAE is usually an outpatient procedure. It is done with numbing medicine at the skin, often with medicine to help you relax. The catheter usually goes in at the groin, and sometimes at the wrist. The procedure often takes about 1 to 2 hours².

After. Most people go home within a few hours. Many teams advise no heavy lifting, straining, or hard exercise for 1 to 2 days. If relief comes, it may start within hours to weeks². Follow your care team's instructions.

What studies show so far

Many early studies reported less knee pain after GAE, but most had no comparison group. In one early single-center, uncontrolled study, about 80% of patients still had meaningful relief 3 years after GAE⁴. In a longer-term study of 46 people, average pain scores fell from about 59 to about 38 out of 100 after 2 years⁵.

Studies without a comparison group cannot tell how much of the benefit comes from GAE itself and how much comes from the placebo effect. That is why sham-controlled trials matter. In these trials, some people get a fake (sham) procedure instead, so researchers can compare.

Sham-controlled trials are mixed so far:

In a small trial of 21 people, pain improved more after GAE than after the sham procedure at 1 month⁶.
In a trial of 59 people, there was no significant difference between GAE and the sham procedure at 12 months⁷.
In a trial of 58 people, there was no significant difference at 4 months or at 12 months^8,9.

A 2025 review of the studies said the benefit over placebo "remains uncertain"¹⁰. Experts disagree about what this means. The Society of Interventional Radiology (SIR), the main U.S. group for interventional radiologists, calls GAE "an established treatment option" and not an experimental one¹. NICE, which reviews treatments in the UK, says the evidence on how well it works is not yet strong enough, so GAE should be used only in research¹¹. More randomized trials, comparing GAE with a sham procedure or with a steroid injection, are still underway¹². Read what each trial found.

Who GAE has been studied in

Most studies included adults over 40 whose knee pain lasted despite at least 3 to 6 months of other treatment. Studies have included mild to severe arthritis on X-rays, but pain tended to improve more in mild to moderate arthritis than in severe arthritis².

SIR describes GAE for people whose pain has not improved with other care and who cannot have, do not want, or want to put off a knee replacement¹. Your doctor can tell you whether your knee and your X-rays fit the people who have been studied.

GAE and knee replacement

GAE does not replace a knee replacement, and some people may still need a knee replacement later². In one study, 9 of 46 people later had a knee replacement, and their surgeons reported no extra difficulty during the operation⁵. It is not yet known whether GAE can put off a knee replacement. Compare GAE and knee replacement.

Can GAE be repeated?

Repeat GAE has not been well studied. One expert review says a second GAE may be considered if the first did not help, about a year after the first one². Ask your doctor what would happen next if your pain comes back.

Risks to ask about

In studies so far, serious problems have been rare, and most side effects went away on their own³. But GAE has risks, like any procedure.

Skin color change over the knee. This is the most common side effect. It happened in about 16 in 100 people in one large review¹³, and it usually goes away within a month¹. It happens when some particles reach small arteries that feed the skin instead of the joint lining².
Knee pain for a short time after the procedure. This happened in about 10 in 100 people¹³.
Less common problems. These include bleeding or bruising where the catheter went in, a blood clot in a leg vein⁵, and, rarely, a small skin sore over the knee (about 3 in 1,000)¹.

Read more about GAE side effects and recovery.

Questions to ask

Does my knee pain and my X-ray fit the people GAE has been studied in?
Which particles do you use, and why?
What results do you see in your own patients, and how do you measure them?
What would we try next if GAE does not help?

Who performs GAE

GAE is performed by interventional radiologists¹. NICE says it should be done only by interventional radiologists with specific training in GAE¹¹. It is fair to ask how many GAE procedures your doctor has done. Read more about interventional radiology.

Common questions

What is GAE?

GAE is a procedure for knee pain from osteoarthritis. A doctor uses a small catheter to place tiny particles in the small arteries around the knee, to slow blood flow to inflamed tissue in the joint lining. It is still being studied.

Is GAE surgery?

GAE is not open surgery. It is done through a small catheter placed in an artery, usually at the groin, with numbing medicine and often light sedation. Most people go home the same day.

Does GAE fix cartilage?

No. GAE targets inflamed tissue and extra blood vessels in the joint lining. It does not rebuild worn cartilage, and some people may still need a knee replacement later.

What is the FDA status of GAE?

No particle used for GAE has an FDA indication for knee pain yet, so in the U.S. their use for knee pain is off-label¹. Several of these particles have received the FDA's Breakthrough Device designation for GAE, which is not the same as approval for that use¹.

Can I have GAE after a knee replacement?

GAE was first used for bleeding into the knee after a knee replacement². It is now being studied for pain that continues after a knee replacement, but there is less research on that use¹⁴. Ask your surgeon and an interventional radiologist.

Bring questions to your visit

A printable list of questions about GAE, with background notes from the sources. Talk with your doctor about these questions.

Questions to ask before GAE

What is genicular artery embolization (GAE)?