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, 77.2% 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 -0.38 to 0.24; and functioning: 0.49, 95% CI -1.34 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.