6 Things to Know About Hyaluronic Acid Injections for Knee Osteoarthritis

Hyaluronic acid (HA) injection, also known as intra-articular hyaluronic acid injection, involves using a needle to inject a gel-like substance between the bones of the joints. The idea is to replace the naturally occurring hyaluronic aid that is depleted as cartilage wears down with time or after an injury—the most common causes of osteoarthritis (OA).

Also known as viscosupplementation, treating knee arthritis with HA injections aims to improve lubrication within the joint in order reduce pain and improve ease and range of motion. Before you consider this treatment, discuss it thoroughly with your rheumatologist, as there are some important things you should know before you agree to have it.

Doctor examining patient's knee
PhotoAlto / Michele Constantini / Getty Images

1) Hyaluronic acid injections are not recommended by major medical organizations.

In 2019 the American College of Rheumatology (ACR) and the Arthritis Foundation (AF) conditionally recommended against treating knee arthritis with intra-articular hyaluronic acid in guidelines for managing OA of the knee, hip, and hand.Similarly, the American Academy of Orthopedic Surgeons does not recommend HA injections for knee arthritis.

This is largely because while replacing lost hyaluronic acid may sound like an easy fix for OA, research has not found this to be the case. In studies comparing hyaluronic acid injections to a placebo (saline injections), the hyaluronic acid has been no more effective than the saline.

Similarly, there is no definitive answer to whether hyaluronic acid injections are any more effective than corticosteroid injections or oral medications. This doesn't necessarily mean you won't be helped with this treatment, but based on studies it's possible you won't.

2) They are not a first-line medical treatment.

Your healthcare provider may want to try hyaluronic acid for you knee OA, but only after more effective treatments haven't relieved symptoms enough. This can be tricky because research has shown that if hyaluronic acid is at all beneficial, the best results usually occur during the early stages of OA.

For treating knee OA, the ACR/AF guidelines strongly recommend other specific approaches: topical and oral non-steroidal anti-inflammatory drugs (NSAIDs) and steroid injections as well as a number of non-medical management strategies such as weight loss, exercise or physical therapy, tai chi, hot or cold therapy, and use of a cane.

Hyaluronic injections typically are not considered unless pain relief medications and steroid injections do not relieve symptoms or become less effective after working for some time.

Conditionally recommended treatments for knee OA are topical capsaicin (in over-the-counter products such as Aspercreme and Zostrix HP) and OTC and prescription oral medications including acetaminophen (the active ingredient in Tylenol), Cymbalta (duloxetine,) and Conzipor or Qdolo (tramadol).

The most significant pain relief from knee osteoarthritis tends to occur eight and 12 weeks after the first injection and can last up to six months or even longer.

3) Hyaluronic acid injections are classified as medical devices.

Interestingly, the Food and Drug Administration (FDA) regards hyaluronic acid injections as class III medical devices, defined as those that "sustain or support life, are implanted, or present reasonable risk of illness or injury." Examples of other class III devices are breast implants and pacemakers.

However, there is some discussion of reclassifying hyaluronic acid injections as drugs, as research has shown they work primarily "through chemical action in the body."

4) Not all hyaluronic acid products are created equal.

Two types of HA are used in intra-articular knee injections: one is derived from rooster combs, while the other is created in the lab using a process that involves bacterial formation. This is important to know if you happen to be allergic to avian (bird) products such as feathers, eggs, or poultry, in which case you could have a serious allergic reaction to any of the hyaluronic acid brands made from rooster combs.

There are eight brands of hyaluronic acid approved by the FDA for treating knee osteoarthritis. Besides how they're made, each differs in how it's administered and how quickly it tends to bring relief. According to the manufacturers, all are effective for up to six months.

Comparison of Hyaluronic Acid Injections
Brand Source   # of injections*
Hyalgan Avian 5
Synvisc Avian 3
Synvisc One Avian 1
Supartz, Supartz FX Avian 3 to 5
Gel-One Avian 1
Orthovisc Avian 3 or 4
Durolane Lab 1 , 3, or 4
Monovisc Lab 1
Euflexxa Lab 3
*Multiple injections are given one week apart.

5) Hyaluronic acid injections cause potential side effects

As with any medical treatment, there's a possibility you'll experience side effects after receiving an injection of hyaluronic acid. The most common ones affect the injection site, including:

  • Residual pain
  • Swelling
  • Redness and warmth
  • Itching
  • Bruising

These tend to be temporary and mild. You can reduce the chances of experiencing side effects by avoiding strenuous activities and resting your knee for the first 48 hours following your injection.

Neither type of hyaluronic acid injections are considered safe for children, pregnant women, and nursing mothers. It's important that your healthcare provider has your complete medical history before they suggest or administer hyaluronic acid to treat knee OA.

If you're taking medication for pain or inflammation of your knee OA at the time of your injection, it's good to know that there should be no adverse interactions between them and the hyaluronic acid. Confirm this with your healthcare provider, but you should not have to stop taking your regular medication.

6) Your Insurance May or May Not Cover Hyaluronic Acid Injections

The FDA has approved hyaluronic acid injections for osteoarthritis of the knee only—not for OA that affects any other joints.

In part because the AAOS does not recommend hyaluronic acid injections for knee OA, there's a strong possibility your insurance company will not cover it. If not, it's important to know the procedure can be quite expensive: A course of three injections of Synvisc, for example, can cost as much as $1,600.

Medicare will cover HA injections for the knee, but you'll likely have to provide documentation or X-ray evidence to prove it's needed first. Both Medicare and private insurance typically will approve hyaluronic acid injections no more often than every six months.

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19 Sources
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