Background: The purpose of this study was to identify predictors of the time from initial presentation to total shoulder arthroplasty (TSA) in patients with primary glenohumeral osteoarthritis (OA) and rotator cuff (RTC) arthropathy who were conservatively managed with corticosteroid injections. Methods: We conducted a retrospective cohort study of patients who underwent TSA from 2010 to 2021. Kaplan-Meier survival analysis was used to estimate median time to TSA for primary OA and RTC arthropathy patients. The Cox proportional hazards model was used to identify significant predictors of time to TSA and to calculate hazard ratios (HRs) with 95% confidence intervals (CIs). Statistical significance was set at P<0.05. Results: The cohort included 160 patients with primary OA and 92 with RTC arthropathy. In the primary OA group, median time to TSA was 15 months. Significant predictors of shorter time to TSA were older age at presentation (HR, 1.02; 95% CI, 1.00–1.04; P=0.03) and presence of moderate or severe acromioclavicular joint arthritis (HR, 1.45; 95% CI, 1.05–2.01; P=0.03). In the RTC arthropathy group, median time to TSA was 14 months, and increased number of corticosteroid injections was associated with longer time to TSA (HR, 0.87; 95% CI, 0.80–0.95; P=0.003). Conclusions There are distinct prognostic factors for progression to TSA between primary OA patients and RTC arthropathy patients managed with corticosteroid injections. Multiple corticosteroid injections are associated with delayed time to TSA in RTC arthropathy patients.