Synovial Fluid Biomarkers Reflect Pre- and Postoperative Clinical Features in Rotator Cuff Tears, Independent of Tear Size.

Synovitis is a major contributor to pain and dysfunction in rotator cuff tears (RCTs), yet it remains unclear whether routine synovial fluid (SF) parameters reflect clinical features independent of tear size, operation method, and patient age. This prospective cohort study aimed to evaluate the associations between routine SF parameters and clinical features before and after rotator cuff repair. Preoperative glenohumeral SF was aspirated from 109 patients undergoing arthroscopic repair, and interleukin-6, total protein levels, and differential white blood cell counts were analyzed. Clinical features, including pain, active range of motion, strength, Constant score, and American Shoulder and Elbow Surgeons (ASES) score, were assessed preoperatively and at 3 and 6 months postoperatively. Associations between SF parameters and clinical features were examined after adjusting for tear size, operation method, and age. Higher interleukin-6 and total protein levels were associated with lower range of motion and functional score, and these relationships persisted at 3 and 6 months. A higher neutrophil percentage was negatively correlated with preoperative range of motion, strength; with range of motion and Constant score at 3 months. Routine SF parameters, including interleukin-6, total protein, and neutrophil percentage, were associated with poorer preoperative clinical features and remained related to early postoperative outcomes. These findings suggest that routine SF parameters are linked to the clinical features of RCT, independent of cuff tear size, operation method, and patient age, and may serve as practical biomarkers for predicting both preoperative and postoperative outcomes.