71 patients with primary glenohumeral osteoarthritis undergoing total shoulder arthroplasty (TSA) were randomized to receive either a subscapularis-targeted rehabilitation program (SR; n=36) or a traditional rehabilitation program plus some subscapularis exercises (TR; n=35). The primary outcome of interest was subscapularis strength. The secondary outcomes of interest included peak, average, and time to maximum isometric strength in internal rotation, incidence of positive belly press, bear hug, and lift-off lag, range of motion (ROM), Patient Reported Outcomes Measurement Information System - Upper Extremity Score (PROMIS), and the American Shoulder and Elbow Surgeone (ASES) score. All outcomes were measured at 3 and 6 months and one year. All outcomes were similar between the two groups at all time points except for PROMIS scores after one year which were significantly better in the SR group.