Objective: To explore the value of musculoskeletal ultrasonography in evaluating the morphological changes of supraspinatus muscle in patients with rotator cuff injury after surgery, in order to provide reference for clinical evaluation of postoperative efficacy.Methods: A total of 95 patients with rotator cuff injury in our hospital from October 2022 to July 2023 were selected, all of which underwent shoulder arthroscopic rotator cuff repair. Musculoskeletal ultrasonography was performed before surgery and 6 months after surgery, respectively, to obtain the morphological parameters of the supraspinatus muscle [supraspinatus muscle cross-sectional area (CSA) and ultrasonic echo intensity (EI)]. The reproducibility of musculoskeletal ultrasound in assessing supraspinatus muscle morphology was analyzed, and the parameters of supraspinatus muscle morphology of healthy and affected side were compared before surgery, as well as those of patients with different injury degrees, and the parameters and changes of supraspinatus muscle morphology of patients with different shoulder joint functional recovery effects were compared before surgery and 6 months after surgery. To analyze the correlation between the morphological parameters of supraspinatus muscle and the functional recovery effect of shoulder joint and the value of predicting the functional recovery effect of shoulder joint.Results: Both the intragroup and intergroup ICC values of CSA and EI were above 0.9 (P < 0.001 for all), suggesting that musculoskeletal ultrasonography had strong repeatability in assessing supraspinatus muscle morphology. CSA on the affected side was lower than that on the healthy side, EI was higher than that on the healthy side (P < 0.05). The CSA in patients with full rotator cuff tear was lower than that in patients with partial rotator cuff tear, and EI was higher than that in patients with partial rotator cuff tear (P < 0.05). The effects of shoulder joint function recovery were as follows: CSA in excellent patients before and 6 months after surgery was higher than that in good patients and able patients; EI in excellent patients before and 6 months after surgery was lower than that in good patients and able patients; CSA and EI in excellent patients were higher than that in good patients and able patients (P < 0.05); Spearman correlation analysis showed that △CSA and △EI were positively correlated with the functional recovery of shoulder joint (r=0.633, 0.693, P < 0.05). The ROC curve results showed that the AUC of △CSA and △EI separately predicted was 0.834 and 0.764, respectively, and that of the combined forecast was 0.922, and the AUC of the combined forecast was larger than that of △CSA and △EI separately predicted (P < 0.05).Conclusion: musculoskeletal ultrasound evaluation of the morphological changes of supraspinatus muscle in patients with rotator cuff injury is closely related to the degree of rotator cuff injury and the effect of shoulder joint function recovery.