Euflexxa is a gel-like injection used to treat knee pain caused by osteoarthritis. It contains sodium hyaluronate, a form of hyaluronic acid that naturally exists in healthy joint fluid. The treatment is given as a series of three injections, one per week, directly into the knee joint. It’s typically reserved for people whose pain hasn’t improved enough with simpler treatments like physical therapy, over-the-counter pain relievers, or steroid injections.
How Euflexxa Works in the Knee
In a healthy knee, the joint fluid is thick and slippery, acting as both a lubricant and a shock absorber. Osteoarthritis breaks down this fluid. The hyaluronic acid molecules in joint fluid become shorter and less concentrated, which makes the fluid thinner and less effective at cushioning the joint during movement. That loss of cushioning is one reason why walking, climbing stairs, and even standing can become painful.
Euflexxa works by restoring some of that lost viscosity. When injected into the knee, it supplements the thinned-out joint fluid, a concept known as viscosupplementation. The added hyaluronic acid helps the joint absorb impact, reduces friction between cartilage surfaces, and supports the cartilage’s ability to bear weight. It’s not rebuilding damaged cartilage, but it is improving the environment inside the joint so that movement is less painful.
Who Qualifies for Treatment
Euflexxa isn’t a first-line treatment. Most insurance plans, including Medicare, require that you’ve already tried and failed at least three months of conservative care before approving viscosupplementation. That conservative care typically includes two tracks: non-drug approaches like physical therapy, exercise, weight management, or using a knee brace or cane, plus over-the-counter medications like acetaminophen, oral or topical anti-inflammatory drugs, or topical capsaicin.
Beyond that, you generally need to have also tried corticosteroid (steroid) injections without sufficient relief, or have a medical reason you can’t receive them. Only after these options have fallen short does Euflexxa enter the picture.
What the Injection Schedule Looks Like
A full course of Euflexxa consists of three injections spaced one week apart. Each injection is given in a doctor’s office directly into the knee joint, usually by an orthopedic specialist or rheumatologist. The procedure itself takes just a few minutes, though your doctor may drain excess fluid from the knee beforehand.
Don’t expect immediate relief. It generally takes four to six weeks after starting the injection series before you feel the full benefit. In clinical trials submitted to the FDA, patients were followed for 26 weeks (about six months) after their first injection, and the Euflexxa group showed significantly greater pain reduction than a placebo group on a standardized walking test. Repeated treatment cycles have been studied and found safe for up to one year.
How It Compares to Steroid Injections
Steroid injections and hyaluronic acid injections like Euflexxa serve the same joint but work differently. Steroids reduce inflammation directly, which means they tend to work fast, often within a few days. The trade-off is that the relief is short-lived: most people feel pain returning within two to three months.
Euflexxa takes longer to kick in but aims for a longer window of relief. One analysis from the Hospital for Special Surgery found that hyaluronic acid injections produced successful outcomes in about 60% of knee osteoarthritis patients. For people who get good results, the relief can last six months or more, making repeat cycles less frequent than steroid shots. The two approaches aren’t necessarily either/or. Many people try steroids first and move to viscosupplementation when those injections stop providing enough relief.
The Egg Allergy Advantage
Several other hyaluronic acid knee injections on the market are derived from rooster combs, which means they contain trace avian (bird) proteins. For patients with allergies to poultry, feathers, or eggs, those products carry a risk of allergic reactions. Euflexxa was the first non-avian-derived formulation, made through bacterial fermentation rather than animal tissue. This makes it a safer option for anyone with those specific allergies.
Common Side Effects
Because Euflexxa is injected directly into a joint, the most common side effects are local. Knee swelling at the injection site is the most frequently reported issue. Other common reactions include headache, diarrhea, nausea, stomach discomfort, itching, and bruising around the injection area. These tend to be mild and resolve on their own.
Less common but more concerning reactions include redness or significant pain at the injection site, skin rash or hives, facial swelling, difficulty breathing, dizziness, or fever. These could signal an allergic reaction or infection and need prompt medical attention. While serious reactions are uncommon, they’re worth knowing about before your first injection so you can recognize them quickly.
What to Expect After the Injections
Most doctors recommend taking it easy for 24 to 48 hours after each injection, avoiding prolonged standing, heavy lifting, or high-impact activity. You can typically return to normal daily activities within a day or two. Some temporary swelling or stiffness in the knee right after the injection is normal and usually settles within a day.
If the first course of three injections works well, you and your doctor can discuss repeating the cycle when pain begins to return. The safety of repeat treatment has been established for up to a year. Not everyone responds equally, though. The 60% success rate means a meaningful number of people don’t get sufficient relief, and for those patients, the next conversation is usually about other options, including surgical approaches like partial or total knee replacement.