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.

The NFL has annual revenue of about $9 billion.

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.

Sports law experts had thought the lawsuits might cost the league $1 billion or more if they went to trial. The NFL had pushed for the claims to be heard in arbitration under terms of the players' labour contract.

The league had also argued that individual teams bear the chief responsibility for health and safety under the collective bargaining agreement, along with the players' union and the players themselves.

Dorsett said each day is getting harder for him, as he struggles with memory problems.

"It's frustrating. Frustrating. And to have a 10-year old daughter who says to her mother, 'Daddy can't do this because Daddy won't remember how to do it,' it's not a good feeling," he said. "I'm glad to see there's been ... acknowledgment that football has had something to do with a lot of the issues us players are going through right now."

In recent years, a string of former NFL players and other athletes who suffered concussions have been diagnosed after their deaths with CTE, including both Seau and Easterling.

While some of those who sued suffered brain ailments, others were worried about future problems and wanted their health monitored.

"I'm relieved; I don't know about pleased. There are probably too many details to work through that we don't all understand yet, quite frankly. But I'm relieved that both sides came together to protect the game we all love and help the players of the past and tomorrow. And to especially help those who need help right now, who have cognitive issues and those whose quality of life has been taken away," said Mark Rypien, the MVP of the 1992 Super Bowl for the Washington Redskins.

He has dealt with depression and memory problems.

"It's a good day, because we're getting help for those who need help," Rypien said, "and a sad day, because we didn't get this done earlier to help guys in the past."

Researchers at the Boston University Center for the Study of Traumatic Encephalopathy, who have been examining brains of deceased NFL players, praised the $10 million set aside for research.

The lawsuits, along with a growing awareness that concussions can have serious long-term effects, have already spurred research into better helmets and changed the way the game is played.

Helmet maker Riddell, which was also sued, was not a party to the settlement. The company declined comment.

The NFL has also instituted rule changes designed to eliminate hits to the head and neck, protect defenceless players, and prevent athletes who have had concussions from playing or practicing until they are fully recovered. Independent neurologists must be consulted before a player can return to action.

One key rule change that takes effect this season bars ball carriers from using the crown of the helmet to make contact with defenders.

"We thought it was critical to get more help to players and families who deserve it rather than spend many years and millions of dollars on litigation," NFL Executive Vice-President Jeffrey Pash Executive Vice-President Jeffrey Pash said in a statement, the only comment issued by the league. "This is an important step that builds on the significant changes we've made in recent years to make the game safer."

AP Pro Football Writers Howard Fendrich and Barry Wilner in New York and AP Sports Writer Nancy Armour in Detroit contributed to this report.