The glenohumeral joint is a complex anatomic structure commonly affected by injury such as tendinopathy and rotator cuff tears. This review presents an up-to-date overview of research on tendon biology and structure, shoulder joint motion and stability, tendon healing, and current and potential future repair strategies. Recent studies have provided information demonstrating the serious impact on uninjured tissues after a rotator cuff tear or other cause of altered shoulder joint mechanics. Another major focus of recent research is biological augmentation of rotator cuff repair with the goal of successfully reinstating normal tendon-to-bone structure. To effectively treat shoulder pathologies, clinicians need to understand normal tendon biology, the healing process and environment, and whole shoulder stability and function.