(CNN) Former Penn State football coach Joe Paterno knew that his assistant coach Jerry Sandusky was sexually abusing a child as early as 1976, according to a new court filing.

This date is 12 years before what had been thought was the earliest known allegation of abuse by Sandusky. The new allegation was revealed in a single line of a court document filed Wednesday -- a judge's order in an ongoing lawsuit brought by Penn State against its former insurance company.

Sandusky was found guilty in 2012 of sexually abusing 10 boys during the 1990s and 2000s. He used a charity he founded and access to the college football team to entice and abuse kids. Sandusky, now 72, was sentenced to a minimum of 30 years.

Paterno's family issued a statement Thursday saying the late coach's "reputation has once again been smeared with an unsubstantiated, forty-year-old allegation."

"Over the past four and a half years, numerous allegations that were taken as fact when they were initially communicated have been proven false. It is in this context that the latest claim should be viewed," the family said.

Read More