The subacromial bursa in rotator cuff injury: from pathological contributor to regenerative resource?

Rotator cuff injury (RCI) represents a leading cause of shoulder pain and functional impairment, imposing a considerable burden on patients' quality of life and healthcare systems worldwide. The subacromial bursa (SAB), a critical anatomical structure located between the acromion and rotator cuff tendons, has traditionally been regarded as a primary pathological contributor to pain generation, inflammation, and tendon degeneration. Aberrant inflammatory signaling, fibrotic remodeling, and nociceptive sensitization within the diseased SAB can disrupt the homeostatic tendon microenvironment and impair intrinsic healing capacity, thereby supporting the historical rationale for routine bursectomy during surgical repair. Paradoxically, accumulating evidence challenges this conventional view, suggesting that the SAB also serves as a biologically active, endogenous regenerative reservoir. It contains mesenchymal stem cells (MSCs) with promising proliferative and tenogenic potential, secretes bioactive growth factors, and modulates the local immune microenvironment to promote reparative and anti-inflammatory responses conducive to tendon healing. This dual biological role presents an important clinical dilemma in arthroscopic rotator cuff repair: should surgeons resect pathological bursal tissue to alleviate the inflammatory burden and improve visualization, or selectively preserved to maintain its potential regenerative capacity? In this comprehensive narrative review, we critically synthesize current evidence regarding the pathological and regenerative functions of the SAB in RCI, critically evaluate the ongoing controversy between bursal resection versus preservation, and summarize emerging SAB-targeted therapeutic strategies. Furthermore, we integrate multi-omics insights into bursa biology aimed at moderating the local microenvironment. Finally, we highlight current translational challenges and future directions to inform biologically guided and evidence-based management of the SAB for rotator cuff repair.