When creating a new illness/injury, the user can select the prognosis date as a forecast of when the athlete will be fit again: 
Adding a prognosis date does not automatically trigger the system to close the illness/injury.
A prognosis date is also shown in the Current State overview on team level:
General info: user functionalities depend on the roles & permissions settings. If a certain functionality does not work within your user account, this will be because you don't have sufficient permissions for this.