Product Differences in Intra-articular Hyaluronic Acids for Osteoarthritis of the Knee

Background: Knee osteoarthritis (OA) is a common and often disabling joint disorder among adults that may result in impaired activity and daily function. A variety of treatment options are currently available and prescribed for knee OA depending on the severity of the disorder and physician preference. Intra-articular hyaluronic acid (IA-HA) injection is a treatment for knee OA that reportedly provides numerous biochemical and biological benefits, including shock absorption, chondroprotection, and anti-inflammatory effects within the knee. Clarity is needed as to whether the available IA-HA products should be considered for therapy as a group or whether there are significant differences in the products that need to be considered in treatment of OA of the knee. Purpose: To determine whether there are differences in efficacy and safety with respect to intrinsic properties of available IA-HA injections for knee OA. Study Design: Meta-analysis. Methods: A comprehensive literature search of the Medline, EMBASE, and PubMed databases was conducted for all existing randomized trials of IA-HA. The primary outcome measure analyzed was the mean pain score at the reported follow-up nearest to 26 weeks after injection. Pooled efficacy and safety results were recorded for subgroupings of HA product characteristics. Results: A total of 68 studies were included for analysis. Products with an average molecular weight 3000 kDa provided favorable efficacy results when compared with products of an average molecular weight <3000 kDa. Products with a molecular weight 3000 kDa demonstrated significantly fewer discontinuations due to treatment-related adverse events than did 1500 kDa counterparts, while trial discontinuation rates were similar between biological fermentation-derived HA products and avian-derived HA. The results did not demonstrate a significant difference in the occurrence of effusion across molecular weight subgroups. Additionally, biological fermentation-derived HA had a significantly smaller incidence of effusion than did avian-derived HA. Biological fermentation-derived HA demonstrated fewer acute flare-ups at the injection site than did avian-derived HA products, while high-molecular-weight products demonstrated the highest rate of injection site flare-up. Conclusion: Despite similarities, IA-HA products should not be treated as a group, as there are differences in IA-HA products that influence both efficacy and safety. In the available literature, IA-HA products with a molecular weight 3000 kDa and those derived from biological fermentation relate to superior efficacy and safetyfactors that may influence selection an IA-HA product for OA of the knee.