Rotofunc - Non-traumatic Shoulder Instability and Total Rotator Cuff Function

The goal of this clinical trial is to test the effect of a novel assessment and treatment strategy for young adults with severely disabling non-traumatic shoulder instability. The main question it aims to answer is if this treatment will substantially change the patients shoulder function to a more stable and controllable state and thereby give a higher quality of life. Participants failure in active shoulder muscle function will be assessed and exercises will be selected individually. Patients will be asked to perform the exercises twice per day. At clinical visits to a specialized physiotherapist the exercises will be upgraded to restore full dynamic stability throughout shoulder movement range. The active treatment period will be 4 months. Researchers will compare two groups. One group will start directly after a baseline assessment is fulfilled. The other group will receive the treat