Predictors of Patient-Reported Outcomes After Hyaluronic Acid Injections: Effect of Expectations and Psychological Stress

Introduction: Hyaluronic acid (HA) injections are a common nonsurgical treatment of knee osteoarthritis (OA). Patient expectations and psychological stress are believed to affect outcomes after orthopaedic procedures. Methods: This was a prospective cohort study seeking to identify factors predictive of greater patient-reported outcomes after HA injections, particularly expectations and psychological stress. 250 patients receiving a series of HA injections for knee OA were enrolled, with 196 being included for analysis. Demographics, surgical history, and preoperative Kellgren-Lawrence severity scores were collected, and patients completed the Knee Osteoarthritis Outcome Score (KOOS) questionnaire, a modified KOOS questionnaire assessing their 6-month postinjection expectations, and the Perceived Stress Scale before the first injection. Outcomes were assessed at 3 weeks and 3 and 6 months after the final injection. Results: KOOS scores improved from preinjection to 6-month follow-up but did not meet patients' expectations or minimal clinically important difference. Expectations correlated with 6-month KOOS pain, activities of daily living, sport, and quality of life subscales (ρ = 0.19 to 0.34), but not the symptom subscale ( P = 0.10). Expectations (ρ = 0.31 to 0.37), younger age (ρ = −0.17 to −0.18), and greater perceived stress (ρ = 0.23) correlated with greater improvement from baseline KOOSs. Lower body mass index (ρ = −0.19 to −0.22), male sex (ρ = −0.17), and greater preinjection function (ρ = 0.37 to 0.46) correlated with greater 6-month outcomes. Stress measured on the Perceived Stress Scale did not correlate with 6-month KOOSs ( P ≥ 0.27). Lower Kellgren-Lawrence severity score was weakly associated with greater 6-month KOOS activities of daily living and sport scores (ρ = −0.15 to −0.16) and greater improvement in the KOOS symptom score (ρ = −0.15). Discussion: This study identified that higher expectations, lower body mass index, younger age, male sex, lower radiographic severity, greater preinjection function, and greater perceived stress are associated with greater patient outcomes after HA injection. Physicians should consider these factors when counseling patients with knee OA about viscosupplementation. Study Type: Prospective Cohort Study (Level of Evidence II).