Longterm Effectiveness of Intraarticular Injections on Patient-reported Symptoms in Knee Osteoarthritis

Objective. We examined the longterm effectiveness of corticosteroid or hyaluronic acid injections in relieving symptoms among persons with knee osteoarthritis (OA). Methods. Using Osteoarthritis Initiative data, a new-user design was applied to identify participants initiating corticosteroid or hyaluronic acid injections (n = 412). Knee symptoms (pain, stiffness, function) were measured using The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). We used marginal structural models adjusting for time-varying confounders to estimate the effect on symptoms of newly initiated injection use compared to nonusers over 2 years of followup. Results. Among 412 participants initiating injections, 772% used corticosteroid injections and 22.8% used hyaluronic acid injections. About 18.9% had additional injection use after initiation, but switching between injection types was common. Compared to nonusers, on average, participants initiating a corticosteroid injection experienced a worsening of pain (yearly worsening: 1.24 points, 95% CI 0.82-1.66), stiffness (yearly worsening: 0.30 points, 95% CI 0.10-0.49), and physical functioning (yearly worsening: 2.62 points, 95% CI 0.94-4.29) after adjusting for potential confounders with marginal structural models. Participants initiating hyaluronic acid injections did not show improvements of WOMAC subscales (pain: 0.50, 95% CI -0.11 to 1.11; stiffness: -0.07, 95% CI -038 to 024; and functioning: 0.49, 95% CI-134 to 2.32). Conclusion. Although intraarticular injections may support the effectiveness of reducing symptoms in short-term clinical trials, the initiation of corticosteroid or hyaluronic acid injections did not appear to provide sustained symptom relief over 2 years of followup for persons with knee OA.