87 patients with small to medium rotator cuff tears and had underwent arthroscopic rotator cuff repair surgery were randomized to receive an injection 1 month post-surgery of corticosteroid (40mg triamcinolone acetate plus 2% lidocaine) or saline for the treatment of pain and improvement of function. Outcomes of interest included the American Shoulder and Elbow Surgeons (ASES) score, pain on a Visual Analog Scale (VAS), the Constant Shoulder Score, range of motion and the rate of rotator cuff re-tear. Outcomes were reported up to a minimum of 3, 6 and 12 months post-operation, however mean follow up time was 23.1 and 27 months for the corticosteroid and saline groups, respectively. Results revealed significantly favourable VAS pain and ASES scores in the corticosteroid group compared to the saline group at 3 months. No differences in Constant score were observed at all time points. Forward flexion, external rotation at 90deg abduction, and external rotation at the side were significantly favourable in the corticosteroid group compared to the saline group at 3 months post-operation. External rotation at the side was further significantly favoured in the corticosteroid group at 6 months. No differences in range of motion were observed in all measurements beyond 12 months. Rate of re-tear at 12 months was not significantly different between the two groups.