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We evaluated whether proinflammatory cytokine expression and myofibroblast recruitment in subacromial bursa was linked to rotator cuff lesions with shoulder stiffness. We analyzed expressions of IL-1β, IL-6, and TNF-α in subacromial bursa and joint fluid collected from 14 patients with cuff tears with stiffness as a study group (Group I) and 14 patients with rotator cuff tears without shoulder stiffness as a control group (Group II) using real-time RT-PCR, immunohistochemistry, and ELISA. Myofibroblast apoptosis in subacromial bursa was analyzed using terminal deoxynucleotidyl transferase -mediated deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) and α-smooth muscle actin immunofluorescence staining. Shoulder function was evaluated using the Constant score. Group I had higher mRNA expression ( p < 0.001) and immunoreactivities ( p < 0.001) of IL-1β. They also had higher levels of IL-1β, IL-6, and TNF-α in joint fluid. Increased IL-1β mRNA expression in the subacromial bursa and IL-1β levels in joint fluid were correlated with a preoperative deficit in shoulder motion ( p < 0.001) and preoperative Constant scores ( p < 0.001). Immunofluorescence observations showed that Group I subjects had more myofibroblasts ( p < 0.001) than Group II. In Group II, a significant correlation was found between apoptotic myofibroblasts and total myofibroblasts ( p = 0.002), but not in Group I ( p = 0.510). Increased expression of IL-1β and myofibroblast recruitment in the subacromial bursa in rotator cuff lesions are linked to shoulder stiffness. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1090-1097, 2008 [ABSTRACT FROM AUTHOR]