According to a security official speaking on condition of anonymity because he was not authorized to speak to the media, the 86-year-old Mubarak suffered the injury when he slipped in the bathroom. He will need surgery to repair a fractured thighbone, the official said.
The former ruler, who is awaiting a retrial in connection with the deaths of protesters during the 2011 uprising that drove him from power, has been confined to the army hospital in a southern Cairo suburb due to health problems.
He was sentenced in June 2012 to life in prison for the protesters' deaths, but an appeals court overturned the sentence and ordered the retrial.
The three were fined a total of nearly $3 million and ordered by the court to repay $17.9 million to the state.
A lawyer for the former president told Egyptian media that his client would need a long period of rest after his injury, adding that Mubarak may not be able to attend an upcoming court session set for July 6.