Paterno, who turns 85 on Dec. 21, is also undergoing radiation and chemotherapy for what his family has said is a treatable form of lung cancer. Son Scott Paterno has said doctors are optimistic about a full recovery from the illness.
Paterno initially hurt his pelvis in August after he was blindsided on the field during preseason practice. It was determined Paterno should remain in the hospital now to facilitate his regimen of cancer treatments while recovering from the pelvis injury, the AP was told.
The person declined to identify the hospital to maintain the family's privacy. An operator at the hospital in State College, Mount Nittany Medical Center, said Sunday there was no patient listing for Paterno.
Paterno was fired last month in the aftermath of child sex-abuse charges against former defensive coordinator Jerry Sandusky, who maintains his innocence. Paterno is not a target of the investigation.
Sandusky is scheduled to appear in court Tuesday after being charged Nov. 5 with the first set of child sex-abuse allegations that dated back to 1994.
Amid mounting criticism that school leaders should have done more to prevent the alleged abuse, trustees dismissed Paterno four days later and accepted school President Graham Spanier's resignation under pressure.
Paterno hasn't spoken publicly since his firing. He was diagnosed with cancer several days later during a follow-up visit to the doctor for a bronchial illness, his family has said.
Scott Paterno told the AP last month the first and only incident reported about Sandusky to his father was in 2002 when- according to a grand jury report - a graduate assistant came to Paterno about an abuse allegation in the team showers.
According to the grand jury report, Paterno testified that he referred the account relayed by the assistant to his superior. Paterno has maintained that a more detailed description of what allegedly occurred in the showers was never passed on to him.
State police Commissioner Frank Noonan's reprimand that school leaders had a moral responsibility to do more than what was legally required raised pressure on the university and trustees.
Paterno has called the allegations against Sandusky troubling and urged the public to let the legal process unfold. He initially announced his retirement Nov. 9, taking effect at the end of the season. He called the scandal "one of the great sorrows of my life. With the benefit of hindsight, I wish I had done more." The trustees fired him anyway, about 12 hours later.
The Nittany Lions' head coach for 46 seasons, Paterno amassed 409 career victories for a Division I record.