Hyaluronic Acid in the Treatment of Osteoarthritis: What is New

Abstract

Hyaluronic acid is a glycosaminoglycan composed of disaccharides of glucuronic acid and N-acetylglucosamine. It is present at high concentrations in mammalian connective tissues. Since the length and concentration of HA decrease in osteoarthritis (AO), intraarticular HA injections began to be used in the early 1970s to restore the rheological properties of synovial fluid. Despite the widespread use of HA, many questions about its mechanism of action and properties remain to be clarified. A literature review presented in this article reveals that HA is a symptomatic slow-acting drug in osteoarthritis (SYSADOA) and that there is insufficient evidence to qualify it as a disease modifying osteoarthritis drug (DMOAD). HA is involved in many mechanisms of action ranging from interaction with mechanosensitive articular pain receptors to its ability to modulate extracellular matrix homeostasis. Although low molecular weight HA has a better safety profile and is slightly superior in in vitro studies and animal experimentation, clinical trials evaluating the efficacy of the drug show insufficient evidence to enable one type of HA to be recommended in preference to any other.