60 patients with an isolated, full-thickness supraspinatus tear were randomized to either receive two postoperative ultrasound-guided injections of platelet-rich plasma or to no adjunct postoperative intervention. Patients were evaluated over a mean of 3.5 years for MRI (Sugaya classification) and clinical outcomes (QuickDASH, Oxford Shoulder Score, and Constant Score). At a mean of 3.5 years, there were no significant differences in clinical scores between groups, with the exception of a greater score on the abduction subscale of the Constant score in the PRP group. MRI outcomes were similar between groups at final follow-up.