84 adult patients with symptomatic isolated interstitial supraspinatus tears were randomized to receive infiltration with platelet rich plasma (PRP) or normal saline. A total of two injections were administered separated by 1 month. The primary outcome of interest was the change in lesion volume. Secondary outcomes of interest included pain on a Visual Analog Scale (VAS), the Single Assessment Numerical Evaluation (SANE), Constant score, the American Shoulder and Elbow Surgeons (ASES) score, the incidence of adverse events and the performance of surgical repair. Follow up was performed at 7 and 12 months after the first injection. Results revealed no significant differences between the PRP and control groups in the change in lesion volume, VAS pain, SANE score, Constant score, and ASES score. The incidence of adverse events was significantly higher in the PRP group. No significant difference in the number of surgical repairs performed was observed between the two groups.