Euflexxa and Synvisc: Hyaluronic Viscosupplements

What You Should Know About These Injection Treatments

Euflexxa and Synvisc are hyaluronic viscosupplements used to treat osteoarthritis of the knee. These are injections into the knee administered by a healthcare specialist, such as a rheumatologist or orthopedic surgeon. They work by supplementing the hyaluronic acid that naturally lubricates the joint.

Knee osteoarthritis is a chronic degenerative joint disease that can cause pain, swelling, stiffness, and loss of motion. If you’ve been diagnosed with osteoarthritis in your knee or knees, there are several treatment options, both surgical and nonsurgical.

Man with pain from knee osteoarthritis

lakshmiprasad S / iStock / Getty Images

Since knee osteoarthritis is a chronic degenerative disease, your healthcare provider may suggest starting with more conservative treatments before progressing to more aggressive or invasive ones. Your healthcare provider may suggest physical therapy and low-impact exercises to improve movement and nonsteroidal anti-inflammatory drugs (NSAIDs) to help with pain and swelling.

Corticosteroid injections have also been used to treat osteoarthritis. If these therapies do not improve your symptoms, viscosupplements like Euflexxa and Synvisc may be prescribed to help ease arthritis pain and promote movement. Your healthcare provider may refer to these injections as "viscosupplementation," which means they help the fluid in your joints.

In some cases, total knee replacement becomes necessary. However, hyaluronic viscosupplements have been shown to delay the necessity of total knee replacement surgery.

How Hyaluronic Acid Injections Help Arthritis

Hyaluronic acid is naturally found in cartilage and the synovial fluid between the joints. In osteoarthritis, hyaluronic acid decreases, thus causing pain, inflammation, and problems with movement.

With hyaluronic acid injections like Euflexxa and Synvisc, hyaluronic acid is injected into the affected joint. These treatments work by providing extra lubrication and cushioning within the knee joints.

There is some debate over the effectiveness of these injections. Some studies have shown that the effects are only marginally different than placebo, but others have shown marked improvement of joint pain and mobility.

The American College of Rheumatology conditionally recommends the use of hyaluronic acid injections in those who have not found relief with other treatments such as NSAIDs or physical therapy. In these cases, patients have experienced pain relief that can last up to six months.

What Is Euflexxa?

Euflexxa is a hyaluronic acid injection used to treat the pain caused by osteoarthritis of the knee. Each Euflexxa treatment consists of three injections given a week apart. To achieve maximum relief, be sure to get all three injections.

Your healthcare provider will administer Euflexxa for you by injecting it directly into the proper location of your knee joint. Each Euflexxa injection contains 2 milliliters (ml) of the medication. If both of your knees are affected and need treatment, your healthcare provider will use one syringe per knee.

What Is Synvisc?

Synvisc is another hyaluronic acid injection used to treat the pain of knee osteoarthritis. There are two versions of Synvisc—Synvisc and Synvisc One. Synvisc One requires only one injection. Synvisc requires three.

Typically, a specialist such as an orthopedic surgeon or rheumatologist will administer the injections for Synvisc over the course of three healthcare provider visits, one week apart. After your injections, you may start to feel relief right away.

However, you need to have all three injections to experience the most benefit. Most people will find that they feel the best eight to 12 weeks after their first injection.

With Synvisc One, most people feel relief after a month. Both treatments can provide pain relief from arthritis for up to six months.

How Euflexxa and Synvisc Are Different

Though Euflexxa and Synvisc are both hyaluronic viscosupplements, there are some differences. Both Euflexxa and Synvisc consist of a three-injection treatment course. However, Synvisc One only requires one injection.

Both treatments are made from sodium hyaluronate and purified, but they use different methods. Euflexxa contains a substance extracted from bacteria cells. Synvisc One uses a substance that comes from chicken combs.

Both Euflexxa and Synvisc are effective at treating the pain and decreased mobility that accompany knee osteoarthritis. When choosing which to use, you may want to talk to your healthcare provider and your insurance company to decide which is best for you.

Sometimes cost can be the deciding factor. You may also want to consider whether you can commit to taking three injections one week apart or if your schedule is better suited for one injection. In that case, treatment with Synvisc One may be your best option.

  • Three weekly injections

  • Sodium hyaluronate made from a substance extracted from bacterial cells

  • Treats osteoarthritis knee pain for up to six months

  • Option of one injection (Synvisc One) or three weekly injections

  • Sodium hyaluronate made from a substance that comes from chicken combs

  • Treats osteoarthritis knee pain for up to six months

Other Hyaluronic Viscosupplements 

There are several other hyaluronic viscosupplements approved by the FDA that have similar mechanisms of action and the same indications for use.

Euflexxa vs. Orthovisc vs. Synvisc

Hyaluronic viscosupplements are meant to restore joint fluid back to its original state, so using a medication that is as similar to synovial fluid as possible makes sense.

In a study comparing these and similar drugs, the structure and properties of Euflexxa and Orthovisc were found to be the closest to those of healthy knee joint fluid.

Synvisc also had similar properties, but a different structure.

Side Effects and Warnings

Like all medications, Euflexxa and Synvisc carry the possibility of side effects. It is important to talk to your healthcare provider about any common side effects that do not go away or become severe. The most common side effects with viscosupplements are:

  • Joint pain
  • Arthritis
  • Pain at the injection site
  • Fluid buildup at the knee


If you have had an allergic reaction to any hyaluronan-based products, you should not use these medications. Signs of an allergic reaction include swelling of the face, tongue, or throat, difficulty breathing or swallowing, wheezing, chest pain, hives, sleepiness, and/or fever.

After your injections, it is recommended that you avoid physical activities like running, hiking, biking, and swimming for at least 48 hours. To keep your knee from swelling, it is also recommended that you avoid standing on your feet for more than one hour at a time.

Synvisc and Euflexxa have not been tested in people under the age of 21 or who are pregnant or nursing. Talk to your healthcare provider if you fall into these categories, as these treatments may not be recommended.

When to Call Your Healthcare Provider

Most side effects from Euflexxa and Synvisc will lessen over time. However, if you experience any side effects that worsen or do not go away, talk to your healthcare provider.

If you experience any of the following symptoms, seek emergency help immediately:

  • Shortness of breath or trouble breathing
  • Swelling of the face or throat

These may indicate a life-threatening allergic reaction.

A Word From Verywell

Living with the pain from knee osteoarthritis can be frustrating, especially if it limits your daily activities. Understanding your treatment options and staying proactive in your treatment plan can help you live a full, active life with osteoarthritis.

Talking to your healthcare provider about your treatment options and staying ahead of the damage caused by osteoarthritis can help you remain active and, in some cases, even delay surgical treatment.

Frequently Asked Questions

  • Is Euflexxa made from rooster combs?

    No, Euflexxa is made from a substance extracted from bacteria cells. Synvisc, another hyaluronic viscosupplement, is made using chicken combs.

  • Is Euflexxa safe?

    Like most treatments, it carries risks of side effects or allergic reactions. It is not safe for anyone with a knee joint infection or a skin disease or infection around the injection site, or anyone with a previous allergic reaction to a sodium hyaluronate product.

  • How painful are Euflexxa injections?

    The injection may be uncomfortable and there may be some temporary pain. Side effects may also include joint pain, back pain, limb pain, muscle pain, or joint swelling.

13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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