Hyaluronic Acid Injections of the Knee: Predictors of Successful Treatment

OBJECTIVES: Knee viscosupplementation yields variable results for osteoarthritis. Establishing patient and treatment factors that predict a favorable response to intra-articular hyaluronic acid (HA) treatment will better guide patient and treatment selection. METHODS: This prospective study evaluated patients presenting with Kellgren-Lawrence grade 1-3 painful, primary knee osteoarthritis. The primary outcome measures were the Western Ontario and McMaster Universities Arthritis Index/ Knee Injury and Osteoarthritis Outcome Score (WOMAC/KOOS) and a standardized visual analog scale (VAS). Surveys were completed at the first and subsequent injections, then at three months post-treatment. Response to treatment was defined according to the Osteoarthritis Research Society International 2004 criteria. RESULTS: We enrolled 135 patients, 102 remained for final analysis. Fifty-seven percent of patients had a positive response to treatment. Factors related to a positive response included those with grade 1 or 2 osteoarthritis (RR=2.17; 95%CI, 1.40-3.37), and those who showed improvement after the first injection (RR=2.22; 95%CI, 1.49-3.31). Seventy-eight percent of people who responded to the first injection had a positive response at follow-up. In multi-variable analysis, those aged 60 or older responded more positively with grade 2 osteoarthritis than those less than 60 years (RR=1.98; 95%CI, 1.18-3.21). Gender, race, BMI, smoking status, HA brand, and initial VAS and KOOS scores were not significant predictors of success in either independent or multivariable analysis. CONCLUSION: Patients with mild to moderate osteoarthritis (grades 1 and 2), and those who responded positively to the first injection were two times more likely to respond positively to the injection series than those with grade 3 osteoarthritis, or those who did not respond initially. Patients aged 60 or older are twice as likely to respond than those less than 60 years for grade 2 osteoarthritis. Judicious patient selection and counseling may improve outcomes associated with intra-articular HA injections.