40 patients, between the ages of 18 and 70 years, with pain in the shoulder and rotator cuff tendinosis or partial tendon tear, were randomly assigned into 1 of 2 groups to compare a subacromial injection of platelet-rich plasma to a placebo injection of saline in terms of pain and shoulder function, 1 year after injection. Both procedures were performed in conjunction with a supervised exercise program. The results of the study indicated that platelet rich plasma injections followed by an exercise program are no more effective at improving quality of life, pain, disability or ROM than placebo treatment with an exercise program, in patients with chronic rotator cuff tendinopathy.