OBJECTIVE: We sought to describe and evaluate longitudinal use of intra-articular injections after treatment initiation among adults with radiographically confirmed knee osteoarthritis (OA).

METHOD: Using data from the Osteoarthritis Initiative (OAI), we included participants with radiographically confirmed OA (Kellgren-Lawrence grade (K-L) > /= 2) in > /=1 knee at baseline. With 9 years of data, 412 participants newly initiating hyaluronic acid or corticosteroid injections with their index visit were identified. For each type of injection initiated, socio-demographic and clinical characteristics were described by patterns of treatments (one-time use, switched, or continued injections). Multinomial logistic models estimated the extent to which patient-reported symptoms (post-initial injection and changes over time) were associated with patterns of injection use.

RESULTS: Of those initiating injections, approximately 19% switched, approximately 21% continued injection type, and approximately 60% did not report any additional injections. For participants initiating corticosteroid injections, greater symptoms post-initial injection were associated with lower odds of continued use compared to one-time users (adjusted odds ratio (aOR) for Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain: 0.91; 95%, confidence interval (CI): 0.83 to 0.99; aORstiffness: 0.77; CI: 0.63 to 0.94; aORphysical function: 0.97; CI: 0.94 to 1.00). Symptom changes over time (e.g., worsened or improved) were not associated with patterns of injections use.

CONCLUSION: After treatment initiation, the proportion of patients switching injection use and one-time users was substantial. Symptoms post-initial injection appear to be associated with patterns of injection use. The extent to which these patterns are an indication of lack of impact on patient-reported symptoms should be explored.