Intra-articular hyaluronic acid (IA-HA) injections are a treatment for knee osteoarthritis (OA), although current literature provides mixed results with regard to their efficacy. We will review a randomized controlled trial (RCT) and subsequent extension trial in order to identify factors that are associated with outcomes in patients with knee OA who received IA-HA.
We used data recorded by the FLEXX trial and extension trial for secondary analysis of potential prognostic factors. Linear regression was used to examine the predictors of outcomes at 6- and 12-month follow-up visits.
Sixty percent of all patients presented with a Kellgren Lawrence (K-L) grade 3. Patients with high baseline outcome scores and a K-L grade 3 demonstrated less response than individuals within an earlier stage of knee OA, although results for both K-L grade 2 and K-L grade 3 patients still showed benefit. Those with more severe radiographic change K-L grade 3 often had a better response with the second series of IA-HA injections. Significantly greater positive response in all outcomes was demonstrated for the patient subgroup classified as K-L grade 2, when compared with K-L grade 3 patients.
The results demonstrate that IA-HA for knee OA was of greater benefit in those with less severe radiographic changes. However, those with more severe radiographic change often had a better response with the second course of IA-HA. Similar analyses are required in order to determine if these results are unique to Euflexxa, or if these results are consistent with other available IA-HA agents.