Objective: To explore the application of platelet-rich plasma (PRP) combined with betamethasone after rotator cuff injury repair and the impact on shoulder range of motion. Methods: A total of 116 patients who underwent rotator cuff injury repair were selected. They were divided into the control group (n=58, receiving betamethasone treatment) and the observation group (n=58, receiving PRP combined with betamethasone treatment) according to different treatment methods. The pain level [Visual Analog Scale (VAS) scores], shoulder joint range of motion (anteflexion and abduction angles) and function [Constant-Murley Shoulder Score (CMS)], inflammatory factors [tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), transforming growth factor-β1 (TGF-β1)] and incidence of adverse reactions were compared between the two groups. Results: At 1, 3, and 6 months postoperatively, the observation group showed a decrease in VAS scores, an increase in shoulder ranges of anteflexion and abduction, and a rise in CMS compared to the control group (P0.05). Conclusion: PRP combined with betamethasone can relieve pain, improve shoulder range of motion, and alleviate inflammatory response in patients after rotator cuff injury repair, with high safety.