The US Supreme Court on Monday rejected the final two challenges to the estimated $US1 billion ($A1.3 billion) settlement between the NFL and thousands of its former players who have been diagnosed with brain injuries linked to repeated concussions.
Players who already have been diagnosed with Lou Gehrig's disease, Parkinson's, Alzheimer's or dementia could begin receiving payments in 90 to 120 days.
"The benefits process will finally move forward," said attorney Christopher Seeger, who represented the class of more than 20,000 retired NFL players now eligible for payments for the next 65 years.
The league has estimated that 6,000 former players - or nearly three in 10 - could develop Alzheimer's disease or moderate dementia.
Payments could be as high as $US5 million ($A6.7 million) for those with Lou Gehrig's disease, also called amyotrophic lateral sclerosis, or ALS; the average payout is expected to be closer to $US190,000 ($A253,000).
"These courageous men and their families, who in the face of great adversity took on the NFL, have made history," Seeger said.
"Despite the difficult health situations retired players face today, and that many more will unfortunately face in the future, they can take comfort in the fact that this settlement's significant and immediate benefits will finally become available to them and last for decades to come."
The class-action lawsuit filed in Philadelphia accused the NFL of hiding what it knew about the link between concussions and chronic traumatic encephalopathy, the degenerative brain disease that has been found in dozens of former players after their deaths.
Senior US District Judge Anita B. Brody approved the deal last year after twice sending it back to lawyers over concerns the fund might run out.
It was upheld by the 3rd US Circuit Court of Appeals in April.
As part of the settlement, the NFL admitted no fault, though a league official did acknowledge during congressional testimony that there is a link between football and CTE. The deal avoids the need for a trial and means the NFL may never have to disclose what it knew and when about the risks and treatment of repeated concussions.
In a statement, NFL spokesman Brian McCarthy said the league was pleased with the decision.
"We look forward to working with class counsel and Judge Brody to implement the settlement and provide the important benefits that our retired players and their families have been waiting to receive," McCarthy said.
