Hyaluronic acid injections for osteoarthritis of the knee: predictors of successful treatment.

PURPOSE: This study aimed to identify patient and treatment factors that predict a favourable response to intra-articular hyaluronic acid (HA) treatment to better guide patient and treatment selection.
METHODS: This prospective, observational study evaluated patients with mild-to-moderate (Kellgren-Lawrence grades 1-3) primary knee osteoarthritis treated between March 2013 and May 2016. Patient function and pain scores were assessed by the Western Ontario and McMaster Universities Arthritis Index/Knee Injury and Osteoarthritis Outcome Score (WOMAC/KOOS) and visual analogue scale (VAS) surveys, with response to treatment defined according to the Osteoarthritis Research Society International (OARSI) 2004 criteria. Surveys were completed at each injection and three months post-treatment. Patients were followed an average of 27 months.
RESULTS: Of 102 patients, 57% had a positive response. Those at least twice as likely to respond were patients with grades 1-2 osteoarthritis or a positive response to the first injection and those who were ≥60 years. Gender, race, body mass index (BMI), smoking status, HA brand, and initial VAS and WOMAC/KOOS scores were not significant predictors of success. Mean time to arthroplasty following injection series was 11 months (30% of nonresponders, 12% of responders). The VAS strongly correlated with KOOS pain scores and successful outcomes.
CONCLUSION: Patients with mild-to-moderate osteoarthritis (grades 1-2) and those responding positively to the first injection were twice as likely to respond positively to the injection series, as were patients ≥60 years. Patients who did not respond positively were more likely to proceed to arthroplasty. The VAS appears to be a reliable method of defining and monitoring treatment success. Judicious patient selection and counseling may improve outcomes associated with intra-articular HA injections.