Intra-articular hyaluronic acid injections are used worldwide to improve pain and function in patients with mild to moderate knee osteoarthritis (OA). “A major drawback of this therapy is that response rates in most trials have been 60% to 70% at best, and predictors of treatment success are unclear”, said Florent Eymard, a rheumatologist at AP-HP Henri Mondor hospital in Créteil (France). To explore risk factors for lack of response, he and his associates studied 166 patients with complete clinical and radiologic data who had participated in a trial of 205 patients with symptomatic knee OA. In this trial, two different hyaluronic acid preparations for intraarticular use were compared. Patients received three weekly intra-articular injections, and those who fulfilled the OMERACT-OARSI criteria six month later were classified as responders. These criteria present the results of changes after treatment in three symptomatic domains (pain, function, and patient’s global assessment).
As the two study arms resembled each other clinically and demographically, data were pooled for the analysis.
The average age of the patients in the subgroup was 65 years. They had about a 49-month history of knee OA, and were typically overweight (mean Body Mass Index (BMI) nearly 28).
At month six, 68% of patients were considered responders, and average pain and total scores on the Western Ontario and McMaster Universities Arthritis Index had fallen by more than 40%. High BMI and severe radiographic narrowing of the tibiofemoral joint predicted lack of response.
Older age and history of viscosupplementation or intra-articular corticosteroid injections showed the same trend, but failed to reach statistical significance. “When we combined these four risk factors, they showed a strong cumulative impact on lack of response”, explained Eymard: Those with two risk factors had less than a 70% response rate, and only 30% of patients with all four risk factors responded to the injections. “Our findings may impact our daily practice and help in considering viscosupplementation in future international recommendations”, Eymard concludes. He recommends that patients older than 65 years, with severe radiological and symptomatic osteoarthritis and no contraindication for surgery or anesthesia, can be referred to a surgeon without prior viscosupplementation. “However, we can continue to consider therapy with hyaluronic acid in patients with severe radiological osteoarthritis, if they are young, have many comorbidities, or refuse surgery”, he concluded.
Source: Eymard F. Predictive factors of failure of viscosupplementation in patients with knee osteoarthritis. Results of a post-hoc analysis of a double blind, controlled non inferiority trial. Abstract OP0135, presented on the 11th of June.