The shoulder is the commonest joint in the body to dislocate. The increased propensity of the glenohumeral joint to dislocate or subluxate stems from its instability, and is due to various bony, joint, and soft tissue characteristics. These factors can be anatomic, biomechanical, post-traumatic, or developmental causes. Imaging serves as the primary tool to confirm the clinical diagnosis and plan management. The spectrum of imaging modalities includes plain radiographs, CT, and MRI. Accurate interpretation of the images by the musculoskeletal radiologist facilitates the orthopedic surgeon in classifying the various types of instability and are detailed in the chapter. Several diagrams and images are included to assist the learner/reader in comprehending the complex concepts and characteristics of shoulder instability.