Washington quarterback Robert Griffin III being hit by Detroit Lions defensive end Corey Wootton on Aug. 20. Griffin left the game with a concussion and did not return. (Ricky Carioti/The Washington Post)

SOME 50 million people are likely to watch Tom Brady take on Peyton Manning in Sunday’s AFC championship game, and an even larger share of the U.S. population will probably tune in to Super Bowl 50 next month. Watching (though not playing) football is the American pastime. One of the few near-universal experiences that remains in the Internet age is enjoying a form of moderately restrained violence.

But, for increasing numbers of fans, that enjoyment is tinged with moral qualm. Seemingly every week brings stories about the awful toll the sport takes on its players. Antwaan Randle El, a former wide receiver for Washington’s professional football team, is not even 40, but he cannot descend stairs normally, has serious memory problems and told the Pittsburgh Post-Gazette this week that he regrets ever playing the game. This month, the Journal of the American Medical Association published a study of a deceased 25-year-old former college football player’s brain, finding that the man, who had suffered more than 10 concussions during 16 years of play, had chronic traumatic encephalopathy (CTE), a debilitating disorder similar to Alzheimer’s disease that scientists have been finding in autopsies of other football players. Before dying of cardiac arrest, the former player dropped out of school and suffered from headaches, anxiety and depression.

Football must change.

Ivy League undergraduates who did not have the “opportunity” to prove their toughness in the Civil War developed the game in the late 19th century. The point was brutality. Football developed over the years in ways that lessened and heightened the various risks — the dangerous “flying wedge” formation was banned, the forward pass became an essential part of the game, helmets were mandated. More recently, the National Football League has imposed concussion protocols, forcing players to sit on the sidelines after a concussion diagnosis, and discouraged head-to-head contact. The league claims it has reduced concussions by a third.

The scandal of the past is the extent to which players were kept ignorant of the risks they were taking, ending up in middle age with severe disabilities — or dead. Now that the risks are clearer, some argue that players are capable of informed consent; if they want to play, let them. Yet researchers still know relatively little about why CTE develops in some athletes’ brains and not in others’. And even if the science were further along, it would not end the ambivalence Americans felt about taking pleasure in a gladiator spectacle.

“I wouldn’t be surprised if football isn’t around in 20, 25 years,” Mr. Randle El said. If it wants to prove him wrong, the NFL will have to reform the game. Some research suggests that teaching proper tackling technique, which may counterintuitively involve banning helmets during practices, could help. Some have suggested speeding up the play clock, which could give coaches less time to dictate dangerous plays. We don’t pretend to know the answers. But pretending no problem exists shouldn’t be an option.