Hidden injuries are created when an athlete is treated for something not connected to an injury.

When a new treatment record is added to the treatment database and you select a body area and body part to treat SportsWare creates a hidden injury record that will appear in the injury database with a grey background(must have dim records and hidden injuries selected in the filters to see this).  

You can change a Hidden Injury record to a regular injury record by selecting the injury, clicking edit and toggle Hidden to No under in the Status section of the injury record.