What Is Hyaluronic Acid?

Hyaluronic acid, also called hyaluronan or hyaluronate is a gel-like substance that is naturally present throughout the human body. In the joints, natural hyaluronic acid has several functions, including:

• Lubrication. Hyaluronic acid binds well to water, producing a viscous, jelly-like consistency. This viscous fluid provides lubrication and also acts as a shock absorber within the joint.
• Growth of cartilage and bone. Hyaluronic acid helps in the growth and development of joint’s cartilage and bone by promoting the growth of new cells and tissues.
• Reducing inflammation. Hyaluronic acid plays an important role in reducing joint inflammation and pain caused by injury or tissue degeneration.

In the joints and in the rest of the body, hyaluronic acid also acts like a moisturizer, keeping tissues hydrated. The body of a person weighing 154 lbs contains approximately 15 oz of hyaluronic acid.¹Carmen G. Boeriu, Jan Springer, Floor K. Kooy, Lambertus A. M. van den Broek, and Gerrit Eggink, "Production Methods for Hyaluronan," International Journal of Carbohydrate Chemistry, vol. 2013, Article ID 624967, 14 pages, 2013. https://doi.org/10.1155/2013/624967. The highest concentrations of hyaluronic acid are found in the joints and the eyeballs, where it helps protect eye lenses.

Producing Hyaluronic Acid

Hyaluronic acid can be commercially manufactured using bacterial fermentation or extracted from certain animal tissues, typically rooster combs.

• Bacterial fermentation: Fermenting the group C streptococci bacteria is the most common method of producing hyaluronic acid on a commercial scale. During fermentation, the bacteria undergo specific treatments to increase their production of hyaluronic acid. The gel is then extracted from the fermentation broth of these bacteria.
• Rooster combs: The most commonly used animal tissue for extraction of hyaluronic is the comb (fleshy crest on the top of the head) of an adult male turkey or chicken. The hyaluronic acid from these tissues needs extensive purification in order to be suitable for human use. The comb tissue extract undergoes various levels of treatments including filtration, drying, and conditioning in order to obtain hyaluronic acid.

Hyaluronic acid is more commonly extracted from bacterial fermentation than rooster combs. The bacterial extract produces higher yield, better quality, and has a lower risk of contamination.¹Carmen G. Boeriu, Jan Springer, Floor K. Kooy, Lambertus A. M. van den Broek, and Gerrit Eggink, "Production Methods for Hyaluronan," International Journal of Carbohydrate Chemistry, vol. 2013, Article ID 624967, 14 pages, 2013. https://doi.org/10.1155/2013/624967.

Uses of Hyaluronic Acid

Hyaluronic acid is used for different types of treatments, such as those for the joints, skin, and eyes.

Hyaluronic acid injections are used for joint treatments. These injections may be intra-articular (within the joint capsule) or periarticular (around the joint capsule). A few joint conditions treated with hyaluronic acid include:

• Osteoarthritis. Hyaluronic acid injections may reduce or relieve inflammation caused by wearing of the cartilage and bone in osteoarthritic joints. The injected gel helps to restore lubrication and also induces the growth of new cartilage and bone tissue in these joints. Osteoarthritis of the knee, shoulder, ankle, hip, and thumb joints may be treated with hyaluronic acid injections.²Hunter DJ. Viscosupplementation for Osteoarthritis of the Knee. Jarcho JA, ed. New England Journal of Medicine. 2015;372(11):1040-1047. doi:10.1056/nejmct1215534^,3Henrotin Y, Raman R, Richette P, et al. Consensus statement on viscosupplementation with hyaluronic acid for the management of osteoarthritis. Seminars in Arthritis and Rheumatism. 2015;45(2):140-149.

  See Hyaluronic Acid Injections for Knee Osteoarthritis

• Frozen shoulder. Hyaluronic acid injections may help relieve stiffness in a frozen shoulder. Research suggests the decreased stiffness may be due to the effects of hyaluronic acid in decreasing inflammation and swelling in the synovial membrane.⁴Gross C, Dhawan A, Harwood D, Gochanour E, Romeo A. Glenohumeral joint injections: a review. Sports Health. 2013;5(2):153-9.
• Rheumatoid arthritis. A recent small study revealed that hyaluronic acid injections may help control inflammation and synovitis in the foot and ankle joints caused by rheumatoid arthritis.⁵Wang C-C, Lee S-H, Lin H-Y, et al. Short-term effect of ultrasound-guided low-molecular-weight hyaluronic acid injection on clinical outcomes and imaging changes in patients with rheumatoid arthritis of the ankle and foot joints. A randomized controlled pilot trial. Modern Rheumatology. 2017;27(6):973-980. doi:10.1080/14397595.2016.1270496

  See Treating Rheumatoid Arthritis (RA) of the Foot and Ankle

• Ankle sprain. Hyaluronic acid injection in a sprained ankle joint may help decrease inflammation and reduce pain.⁶Coronel P, Gimeno M, Petrella RJ. THU0566 Management of Ankle Sprain with Single Periarticular Injection of Sodium Hyaluronate. Annals of the Rheumatic Diseases. 2014;73(Suppl 2):378.2-378. doi:10.1136/annrheumdis-2014-eular.4875
• Tennis elbow. Chronic degeneration of the lateral epicondyle tendon causing tennis elbow may be treated with hyaluronic acid injection in the elbow joint.⁷Petrella RJ, Cogliano A, Decaria J, Mohamed N, Lee R. Management of Tennis Elbow with sodium hyaluronate periarticular injections. Sports Med Arthrosc Rehabil Ther Technol. 2010;2:4. Published 2010 Feb 2. doi:10.1186/1758-2555-2-4^,8Bernetti A, Agostini F, Federica A, et al. "Hyaluronic Acid Injections in the Management of Tendinopathies. A Descriptive Review". EC Orthopaedics 9.4, 2018; 225-232.

Hyaluronic acid is most commonly used in the treatment of knee osteoarthritis. Some doctors may also recommend the use of hyaluronic acid oral supplements with or without injections while treating osteoarthritis. Research suggests taking oral supplements of hyaluronic acid may help treat some osteoarthritic patients with mild knee pain.⁹Oe M, Tashiro T, Yoshida H, et al. Oral hyaluronan relieves knee pain: a review. Nutr J. 2016;15:11. Published 2016 Jan 27. doi:10.1186/s12937-016-0128-2

See Do Hyaluronic Acid Injections Work for Knee Osteoarthritis?

In addition to treating joint pain, hyaluronic acid is widely used in the cosmetic industry to treat dry and/or aging skin. In addition, eye drops containing hyaluronic acid are sometimes used in eye surgeries and for hydrating dry eyes.

Approved use of hyaluronic acid
The US Food and Drug Administration (FDA) approves the use of hyaluronic acid injections for treating knee osteoarthritis, certain types of dermal fillers, and during certain eye surgeries.

See Hyaluronic Acid Injection for Knee Osteoarthritis: Procedure and Risks

The use of HA injections is not advised in children, women who are pregnant or breastfeeding, or for those who have infections at the site of treatment or a known allergy to hyaluronic acid. Hyaluronic acid treatment is also not advisable for people with cancer or a history of cancer.¹⁰Simone P, Alberto M. Caution Should be Used in Long-Term Treatment with Oral Compounds of Hyaluronic Acid in Patients with a History of Cancer. Clinical Drug Investigation. 2015;35(11):689-692. doi:10.1007/s40261-015-0339-x