A minimally invasive treatment could provide relief for people with knee osteoarthritis, a degenerative joint condition that affects millions of Americans.

The procedure involves blocking certain arteries in the knee in order to reduce inflammation that occurs with osteoarthritis.

The procedure doesn’t repair the injury. It simply reduces pain and improves flexibility.

In a small, multicenter clinical trial, researchers found that the majority of patients treated had reduced pain and improved knee function up to a month after treatment.

In the first U.S. clinical trial of the treatment, known as geniculate artery embolization (GAE), researchers recruited 13 people with severe pain due to osteoarthritis in the knee.

Doctors inserted catheters into key arteries in the knee through small incisions in the skin, using medical imaging to guide their work. They then injected microspheres into the arteries, which blocked the flow of blood.

This outpatient procedure took 45 to 90 minutes and didn’t require hospitalization or follow-up physical therapy.

Researchers checked the progress of eight of the patients one month after treatment. All of them had decreased pain, reduced joint stiffness, and improved physical function in the knee.

“This treatment works on its own and the pain relief experienced by patients is due to GAE itself, which improved outcomes immediately without pain medication or physical therapy,” said Dr. Sandeep Bagla, director of interventional radiology at the Vascular Institute of Virginia and lead author of the study.

None of the 13 patients reported any major problems resulting from the procedure.

The research was presented today at the Society of Interventional Radiology’s annual scientific meeting in Los Angeles.

The findings have not yet been published in a peer-reviewed journal.

A common ailment

The Arthritis Foundation reports that about 27 million Americans have osteoarthritis. This condition can affect any joint, but often occurs in the knees, hips, lower back, and hands.

Osteoarthritis can occur in people of all ages, but it is most common in people over the age of 65.

Risk factors include age, obesity, injury to the joint, weak thigh muscles, and genetics.

In healthy joints, cartilage helps the joint move smoothly. In osteoarthritis, the cartilage breaks down, which leads to pain, swelling, and difficulty moving the joint.

As the condition worsens, the bones may also break down around the joint. Severely damaged joints may need to be surgically repaired or replaced.

The most common treatments for osteoarthritis include medications to relieve pain or reduce inflammation.

These all have side effects and risks, especially with long-term use.

Other research has shown success with this procedure, including a Japanese study published in 2014. So far, however, the treatment has only been used in clinical trials.

If additional research shows that GAE is safe and effective, it would provide another treatment option for people with osteoarthritis.

How blocking arteries relieves pain

GAE focuses on blocking arteries in the knee because researchers suspect that chronic inflammation in the joint causes new blood vessels to form.

The blood vessels grow into the cartilage, the synovial membranes that line the joint capsule and the nearby bone — bringing new sensory nerves with them.

Blocking these newly formed vessels may interrupt the cycle of inflammation and damage, which reduces symptoms such as pain.

The data presented at today’s meeting focused on patient outcomes after one month.

Another non-peer-reviewed study presented at the meeting followed 37 patients for an average of two years. Of these, 86 percent reported improved symptoms.

One-third of the 72 patients treated in this study, though, had to undergo the procedure a second time. Repeat procedures would increase the cost of treatment.

Some researchers have estimated that GAE is more expensive than most “conservative” drug treatments for mild-to-moderate knee osteoarthritis, even when taking into account future complications.

But they point out that additional long-term data is needed to be able to compare the true costs of GAE to other procedures.

Compared to open surgery for severe knee osteoarthritis, however, GAE has many things going for it.

“When we compare GAE to things like knee replacement surgery, that have a recovery time anywhere from four to six weeks and are fairly intensive, this doesn't require that kind of recovery,” Bagla told Healthline. “Based on these comparisons, we anticipate that GAE will be a cost-effective option for treatment of osteoarthritis in the knee.”