The shoulder complex is one of the most elaborated joints of our body, as it is formed by several bones (clavicle, scapula, humerus and sternum) that constitute different joints (sternoclavicular, acromioclavicular, glenohumeral, scapulothoracic). The shoulder is the most mobile joint of our body, and its stability is maintained by passive (e.g.: capsule, ligaments, labrum, etc.) and active-dynamic (muscles) stabilisers. Due to its great degrees of freedom, the shoulder is among the most common joints afflicted by “instability”. Shoulder instability can be defined as the loss of functioning and comfort of the shoulder joint due to an excessive translation of the humeral head in the joint socket. Based on its aetiology, shoulder instability is typically classified in one or more of the following categories: a) instability dictated by trauma with clear structural damages to the joint; b) structural deficit without specific trauma; c) absence of structural deficit, likely correlated to muscle patterning imbalance. Patients can report different directions of instability, including anterior, posterior, inferior, and multidirectional. Patients affected by this injury typically present pain localised around the shoulder that can radiate to other structures, instability, loss of confidence, clicking, catching, apprehension, weakness, and impacted shoulder-arm functioning.
