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Orthopedic Injections

Gel Hyaluronic Acid Injections

What is gel hyaluronic acid?

The normal knee joint contains approximately a teaspoonful of fluid that serves to lubricate the moving surfaces and to provide nutrition to the cartilage and meniscus tissues.  One of the components of the healthy “synovial” fluid contains a sugar molecule called hyaluronan, which is a complex sugar that is slippery and gel-like because of its ability to pull in water molecules around it.  Hyaluronan plays a large role in creating a smooth, gliding path for joint motion, much like the oil in a car engine.

When arthritis sets in, the breakdown inside the joint causes a reaction (inflammation) where a watery, abnormal fluid is created that is deficient in the normal hyaluronan found in healthy knees and shoulders.  This causes more susceptibility to further injury to the joint from impact and friction, further worsening the joint destruction.  The concept behind gel injections is that by administering artificial hyaluronan into the joint, the viscosity and slippery nature of the normal synovial fluid can normalize, hence the term “viscosupplementation”.

Gel hyaluronic acid injections are FDA-approved for use in the knee and are considered experimental for the shoulder.  Most data and clinical experience suggests that patients with mild to moderate forms of osteoarthritis are better candidates with greater rates of improvement with viscosupplementation than patients with severe, end-stage bone-on-bone disease(1).  Different theories exist as to why patients with more severe disease do not fare as well with gel injections, but it may relate to the advanced loss of the cartilage padding with nowhere for the injected material to go as well as more substantial abnormality of the arthritic fluid existing in the knee at the time of injection.

While high-quality evidence supporting the use of gel hyaluronic acid injections is lacking, there is good evidence that these treatments can provide a statistical benefit in a subset of patients that have failed other treatments(1).  Most of the improvements in patients that do well with gel hyaluronic acid injections experience relief at 6 weeks and 3 months following injections.  If the injections help, they can be repeated in 6 month intervals, or twice per year.

Viscosupplementation injections are usually performed with a minor numbing injection or spray followed by a brief fullness and soreness during the injection.  These injections are commonly given once a week over three weeks, or sometimes as a single injection of a higher volume.  Icing, elevation, and modifying activity is recommended for the few days following the injection.

These injections are considered very safe, as the sugar molecule that comprises the injection is inert and manufactured in a laboratory.  Infrequently, patients may experience an allergic-type reaction to one or more of the components of the injection that can cause pain and swelling for a few days(2).  This is commonly self-limited and resolves on its own but occasionally can require more urgent medical care.  Rarely, infection can occur as with any injection.


  1. American Academy of Orthopaedic Surgeons Management of Osteoarthritis of the Knee (Non-Arthroplasty) Evidence-Based Clinical Practice Guideline (3rd Edition).  https://www.aaos.org/oak3cpg Published August 31, 2021.
  2. Puttick MP, Wade JP, Chalmers A, Connell DG, Rangno KK. Acute local reactions after intraarticular hylan for osteoarthritis of the knee. J Rheumatol. 1995 Jul;22(7):1311-4. PMID: 7562764.
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Dr. Thomas Obermeyer

  • 15+ years of training and experience treating complex shoulder and sports medicine conditions
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