PHILADELPHIA — The NFL agreed to pay more than three-quarters of a billion dollars to settle lawsuits from thousands of former players who developed dementia or other concussion-related brain disorders they say were caused by the very on-field violence that fueled the game’s rise to popularity and profit.

The class-action settlement, unprecedented in sports, was announced Thursday after two months of court-ordered mediation and is subject to approval by a federal judge. It came exactly a week before the first game of the 2013 season, removing a major legal and financial threat hanging over the sport.

U.S. District Judge Anita B. Brody in Philadelphia is expected to rule on the settlement in two to three months but said it “holds the prospect of avoiding lengthy, expensive and uncertain litigation, and of enhancing the game of football.”

More than 4,500 former players, some of them suffering from depression or dementia, accused the NFL of concealing the long-term dangers of concussions and rushing injured players back onto the field, while glorifying and profiting from the bone-crushing hits that were often glorified in slow motion on NFL Films.

“Football has been my life and football has been kind to me,” said former Dallas Cowboys running back Tony Dorsett, one of at least 10 members of the Pro Football Hall of Fame who filed suit since 2011. “But when I signed up for this, I didn’t know some of the repercussions. I did know I could get injured, but I didn’t know about my head or the trauma or the things that could happen to me later on in life.”

The settlement applies to all 18,000 past NFL players and spouses of those who are deceased — a group that could total more than 20,000 — and will cost the league $765 million, the vast majority of which would go to compensate athletes with certain neurological ailments, plus plaintiffs’ attorney fees. It sets aside $75 million for medical exams and $10 million for medical research.

Individual payouts would be capped at $5 million for men with Alzheimer’s disease; $4 million for those diagnosed after their deaths with a brain condition called chronic traumatic encephalopathy; and $3 million for players with dementia, said lead plaintiffs’ lawyer Christopher Seeger.

The settlement does not include an admission from the NFL that it hid information from players about head injuries. Commissioner Roger Goodell told pro football’s lawyers to “do the right thing for the game and the men who played it,” according to a statement by the league.

Goodell was not made available for comment.

In addition to Dorsett, the plaintiffs include Super Bowl-winning quarterback Jim McMahon, who suffers from dementia; former running back Kevin Turner, who has amyotrophic lateral sclerosis, or Lou Gehrig’s disease; and the family of All-Pro selection Junior Seau, who committed suicide last year.

Turner, who played for the New England Patriots and Philadelphia Eagles, predicted that most of his peers would support the settlement.

“Chances are … I won’t make it to 50 or 60,” said Turner, now 44. “I have money now to put back for my children to go to college and for a little something to be there financially.”

All former NFL players are eligible to seek care, screening or compensation, whether they suffered a documented concussion or not. The amounts they receive will be based on their age, condition and years of play. They do not need to prove that their health problems are connected to playing football.

Players’ lawyers said they expect the fund to cover the ex-athletes’ expenses up to age 65. Current players are not covered.

If the settlement holds, the NFL won’t have to disclose internal files that might reveal what it knew, and when, about concussion-linked brain problems.

“I think it’s more important that the players have finality, that they’re vindicated, and that as soon as the court approves the settlement they can begin to get screening, and those that are injured can get their compensation. I think that’s more important than looking at some documents,” said lawyer Sol Weiss of Philadelphia, who filed the first lawsuit on behalf of former Atlanta Falcon Ray Easterling and a few others. Easterling later committed suicide.