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What are Hyaluronic Gel Injections?

This term has been used to describe a non-operative injection treatment for arthritis of the knee.  The active ingredient in a viscosupplement is Hyaluronic Acid, also known as “rooster comb” or “gel injection”.  This is a naturally occurring product that your body’s joints produce.  Any joint in your body has a layer of tissue surrounding it call the capsule.  This capsule contains the synovium, which are cells in your body that produce the hyaluronic acid.  These cells normally produce this in addition to collagens and other ingredients and secrete these products into the fluid that lubricates the cartilage surfaces of your joints.  Hyaluronic acid owes its excellent lubrication effects to the underlying coil-like structure that is has.  This allows it to trap 1,000 x its normal weight in water.  Think of synovial fluid as not only lubrication, but also a shock absorber.  Research also indicates that hyaluronic acid can play an important role in inhibiting pain signals to the brain, inhibiting enzyme-mediated cartilage destruction and thus decreasing the progression of arthritis and inflammation.

In the setting of osteoarthritis, the synovial cell’s production of hyaluronic acid is altered so that it isn’t producing very much and the quality of the product is diminished.  This in turn leads to a decreased viscosity of the synovial fluid and in turn can lead to progressive cartilage damage.  Some research indicates that your body’s production of hyaluronic acid can be stimulated, or increased, when you undergo injection therapy with a viscosupplement.



How is Hyaluronic Acid produced and are there side effects?

Balazs and colleagues first described the properties of hyaluronic acid in the 1960’s.  The first FDA-approved injectable form of hyaluronic acid was Hyalgan, which came to market in 1997.  This is harvested from rooster combs, which have a high level of naturally produced hyaluronic acid.  There are several other products on the market that have been approved for injection therapy.  Some of them extract the product from rooster combs and others use bacteria to harvest this ingredient.

Some people may experience some localized discomfort after the injection.  A severe reaction could be pseudosepsis, which can lead to severe pain and stiffness.  In lab studies, this complication seemed to happen more often if a large volume was used.  A rare complication with any injection therapy is a septic joint, or infection in the knee.  Pregnant women or nursing mothers should avoid the use of this product.  People with a documented allergy to chickens or bird feathers should also use caution with these products.  Please consult your doctor’s office for any further recommendations.


How long can I experience improvement in symptoms?

A study published in 2011 by Bannuru et al demonstrated that the treatment effect of viscosupplementation reached its peak at around 8 weeks.  There was a detectable effect in patients for up to 6 months.  Many insurance companies have used this as a guideline for duration of time used before authorizing approval for a second or subsequent injection series and require patients to wait 6 months in between series.


Is Viscosupplementation covered under my insurance benefits?

The utility of viscosupplementation and its treatment effects has been called into question in some studies and reviews.  As a matter of fact, some societies such as the AAOS, or American Academy of Orthopedic Surgeons, have recommended against using viscosupplementation.  Despite this recommendation, there are several surgeons and leaders within the field of orthopedics that continue to use these treatments in their practice.  They point to the fact that more recent studies have indeed shown benefit related to viscosupplementation and the fact that these injections were looked at as a whole rather than stratified based on molecular weight, which differs amongst the products.  As a matter of fact, a recent meta-analysis in the Cochrane Review found an overall benefit for viscosupplementation in comparison to placebo for pain, function and patient reported outcomes.  They also found these injections to be equivalent to systemic treatments such as oral anti-inflammatories like Ibuprofen; however, with less systemic side effects.  Several insurance companies have started to deny their members the benefit of viscosupplementation based on some society recommendations.  Check with our office to determine if you are eligible for viscosupplementation.

  1. Smith, M. M. & Ghosh, P. The synthesis of hyaluronic acid by human synovial fibroblasts is influenced by the nature of the hyaluronate in the extracellular environment. Rheumatol. Int. 7, 113–122 (1987).
  2. Bannuru, R. R., Natov, N. S., Dasi, U. R., Schmid, C. H. & McAlindon, T. E. Therapeutic trajectory following intra-articular hyaluronic acid injectionin knee osteoarthritis. Osteoarthritis and Cartilage 19, 611–619 (2011).
  3. Bowden, D. J., Byrne, C. A., Alkhayat, A., Eustace, S. J. & Kavanagh, E. C. Injectable Viscoelastic Supplements: A Review for Radiologists. American Journal of Roentgenology 209, 883–888 (2017).
  4. Hunter, D. J. Viscosupplementation for Osteoarthritis of the Knee. N. Engl. J. Med. 372, 1040–1047 (2015).
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  6. Romeo, A. A., Bert, J. M. Is It Time To Revisit Viscosupplementation Guidelines – Commentary. Orthopedics Today. Dec 2017