Sandusky's son details abuse claims

The adopted son of former American football assistant coach Jerry Sandusky has spoken on television about alleged sexual abuse at the hands of his father.

Matthew Sandusky has told Oprah Winfrey about abuse he says occurred when Jerry Sandusky would tuck him in during overnight stays at the Sandusky home in Pennsylvania, after being instructed to wear only underwear or blue mesh shorts.

Jerry Sandusky would tickle, blow on his belly and wrestle on the floor, he said, and the encounters would gradually become more sexual.

"Then it's, then as I now know, it's oral sex," he said on Oprah Prime.

The claim of oral sex was specifically denied in an audiotape of his 29-minute interview with police detectives that NBC obtained at the time of the 2012 trial of Jerry Sandusky, a former assistant football coach at Pennsylvania State University.

Matt Sandusky told investigators two years ago that Jerry Sandusky had rubbed along or against his genitals but that he did not recall any penetration or oral sex. He said then that he was getting therapy and memories were coming back to him.

He told police he came forward to correct the record from his own grand jury testimony.

"So that they can really have closure and see what the truth actually is. And just to right the wrong, honestly, of going to the grand jury and lying," Matt Sandusky said two years ago.

He was not called to testify, and Jerry Sandusky has not been charged with any crime in relation to his adopted son.

Matthew Sandusky said he recognised elements of his own abuse when he sat through courtroom testimony by a young man described in court as Victim 4.

Sandusky was convicted of abusing 10 boys, including all eight who testified, and is serving a 30- to 60-year sentence. He has lost an appeal to the state Supreme Court.

Matt Sandusky is among those who have shared $US60 million ($A64.92 million) worth of civil settlements by Penn State.