Maggio will undergo surgery this week.
"Christian has suffered meniscal pain for some time," Massimo Briaschi told TeleClubItalia.
"But I visit to the doctor this time showed the need to operate. It is only a small thing though and is nothing to worry about.
"He is one to stay silent and keep on working, that's why it's come to this situation.
"There is no risk that he will miss the World Cup. I'm sure he'll be back after the international break [in October]."