Former Washington Redskins quarterback Joe Theismann, 1975. (Paul Vathis/ Associated Press)

It’s official now: Joe Theismann can boast the most nauseating injury in professional football.

No, not the career-ending fracture of his leg under the bulk of New York Giant Lawrence Taylor in 1985. Not the two front teeth knocked out in a 1982 game. No, we speak of the time the veteran Redskins quarterback got hoof-and-mouth disease.

Well, maybe not hoof-and-mouth disease. But something incredibly gross, anyway.

We’ve been cringing ever since the 1983 Super Bowl winner first shared the story Friday on our colleague Mike Wise’s 106.7 radio show: He was playing a game in 1971 in Montreal with the Canadian Football League, in a stadium that had hosted a cattle show the day before. One thing leads to another — dirt gets in his mouth, and the next day, “all of a sudden, if I drank a glass of water it was like drinking a ball of fire.” (Read a longer account of the story at Dan Steinberg’s Sports Bog.)

Theismann in 2010. (Scott A. Miller/ Associated Press)

The diagnosis is a little vague: Theismann told us Tuesday the dentist told him he had hoof-and-mouth disease or trench mouth. Which turn out to be two different things.

“Theoretically it’s possible” that Theismann had hoof-and-mouth, said Paul Roepe, director of the infectious disease program at Georgetown. “But it’s extremely rare.”

Hoof-and-mouth is a viral ailment, sometimes fatal, that mostly strikes livestock. It’s distantly related to the hand-foot-and-mouth disease that strikes children. You get it from inhaling, though. Whereas trench mouth is a nasty bacterial infection — and yes, you can get it from dirt.

“You basically get it by not taking care of your mouth very well,” Roepe told us.

Of course, there’s a reason this story is coming out now: Theismann, 61, recently signed on as pitchman for Defense Sport Mouthguard Rinse. He told us he takes endorsement deals only with products whose purpose he can relate to — and when he was offered this one, he immediately flashed back to the day he could have used some disinfecting.

“The importance of wearing a mouth guard, and the importance of having it clean — that's what got me excited about it,” he said. (He wasn’t wearing a mouth guard that day in Montreal.) But do not fear, general public: You cannot catch whatever-it-was from Joe Theismann. “I’ve had no recurrence of it since then,” he said.