The official said the 86-year-old Mubarak slipped in the bathroom and broke the upper part of his thigh bone, adding that he would need surgery. The official spoke on condition of anonymity because he was not authorised to talk to media.
Mubarak, toppled in 2011 amid massive protests against his nearly three-decade rule, is facing a retrial for his role in the killing of hundreds of protesters during the uprising.
Mubarak was found guilty in June 2012 of failing to stop the killing of more than 900 protesters during the 18-day revolt and sentenced to life imprisonment, but his conviction was overturned in January 2013. That decision was appealed by prosecutors, and a retrial began in April 2013.
He was ordered released in August last year pending his graft trial, but was kept at a military hospital in a suburb south of Cairo. Given his poor health, Mubarak is likely to serve his sentence in the hospital.
Last month Mubarak was convicted on charges of embezzling millions of dollars of funds allocated for the renovation of presidential palaces. Mubarak's two sons, one-time heir apparent Gamal and wealthy businessman Alaa, were also convicted of graft and sentenced to four years in prison each in the same case.
They have all been held since 2011 but only time in custody in connection with the graft case - about a year since the charges were raised - will be deducted from the sentences.