Metabolic Functions of the Subacromial Bursa: Implications for Shoulder Health and Pathology.

» Historically viewed as a passive structure in shoulder pain, the subacromial bursa (SAB) is now understood to have metabolic function and to be an active participant in shoulder health by influencing cytokine production and cellular signaling pathways.» The variability in the SAB anatomically, along with its varied cell types, makes it an important consideration for shoulder health. Synoviocytes, mesenchymal stem cells, fibroblasts, and immune cells from the SAB can largely influence shoulder pathology.» The SAB influences metabolic function through the release of bioactive molecules such as interleukin-1, interleukin-6, tumor necrosis factor-ɑ, transformation growth factor, and basic fibroblast growth factor. These molecules alter shoulder health by modulating the immune/inflammatory response and promoting angiogenesis, cell proliferation, and fibrosis.» The SAB and its metabolic function are indicated in several clinical conditions, such as subacromial impingement syndrome, shoulder osteoarthritis, subacromial bursitis, and rotator cuff tears, demonstrating its importance and clinical utility.» Further understanding of the SAB and its metabolic function as opposed to its anatomical function allows for novel targets and therapeutics in shoulder pathologies that integrate the field of orthopaedics and immunology. Further studies demonstrating the role of the bioactive molecules released by the SAB and its effect on surrounding tissues are paramount for breakthroughs in shoulder health.» In this study, we present a narrative review of the current understanding of the metabolic function of the SAB.