Silva broke his left leg while throwing a kick at middleweight champion Chris Weidman early in the second round of their rematch Saturday in the main event of UFC 168 at the sold-out MGM Grand Garden.
He underwent surgery after the bout at a local hospital, UFC president Dana White said.
Silva whipped a hard kick at Weidman, who checked it. Silva's bone instantly snapped just above the ankle, as Silva collapsed in agony and Weidman backed off.
The fight ended at 1:16 of the second round and Weidman retained the title via technical knockout, since Silva couldn't continue. Doctors and paramedics placed a splint on his left leg and removed him from the cage on a stretcher.
Weidman checked the kick with a technique he learned from coach Ray Longo.
"Ray Longo once broke a guy's leg in training using what he calls 'The Destruction,' " Weidman said. "It's knee on shin, so when he goes to kick, you put your knee on his shin. It has happened in sparring and guys take a minute off and walk around, and at least it stops them from kicking you.
"To break someone's leg, I've never done that before. I didn't want to see Anderson get hurt like that."
Silva's injury was reminiscent of a 2008 broken leg Cory Hill suffered during a fight in North Carolina against Dale Hartt. Hill's bone broke through the skin and his foot was facing the wrong way when he hit the ground, but he returned to action 13 months later. However, his status is very different than Silva's and it's not likely that Silva will go through the ordeal it will take to return.
Silva had already contemplated retiring. Given the injury, his age and his stature in the sport, it would be a daunting task for him to get back to competition. If he could make it in 13 months like Hill, he'd be nearly 40-years-old and would have to fight young, hungry stars in order to battle his way back into contention.
That can't be appealing for a legend like Silva, who holds a slew of UFC records and is widely regarded as the greatest MMA fighter of all-time.
His injury caused the heavily pro-Silva crowd to gasp in horror. Even rival Vitor Belfort was disappointed.
"I feel for Anderson," said Belfort, who will fight Weidman for the title sometime next year.
Silva nearly didn't make it to the second round. Early in the first, Weidman caught him with a short right hand on the inside that nearly knocked the ex-champion out. Silva's eyes rolled back in his head and Weidman pounced in an attempt to go for the finish.
Weidman landed several nasty elbows from the top position, but the wily veteran recovered and made it through the round.
It wasn't a good sign, though, because he did little offensively and took a great deal of punishment. Weidman, though, was impressed with what he saw of Silva in their brief time in the cage Saturday.
"He's never shown signs of slowing down, so I couldn't afford to think that because he's getting older this would be the fight where it would start showing," Weidman said. "I expected the best Anderson Silva and I actually thought he looked great tonight. Physically, I thought he looked the best I've ever seen him."
Silva's presumed departure will leave the company without two of the greatest stars of its boon era. The UFC was struggling and in peril of collapse until the success of "The Ultimate Fighter" Season 1 finale. Silva and Georges St-Pierre became the biggest stars of the era and now, each is gone at least for a while.
St-Pierre abdicated his welterweight title and announced he'd take a sabbatical following UFC 167 last month. St-Pierre said he had been burned out by dealing with the pressure and needed to handle some personal issues.
Silva's departure is more sudden, shocking and heartbreaking for those who reveled in his greatness, and the UFC will now have to find new stars.
That's the fight game, however. In boxing, fans would fret about what would happen to the sport when Muhammad Ali left, and then Sugar Ray Leonard came along. And then, as Leonard's career was winding down, Mike Tyson became not only the biggest thing in boxing, but one of the biggest names in sport.
After Tyson, Oscar De La Hoya took over and once De La Hoya was gone, Floyd Mayweather Jr. became the face of the sport.
The UFC will overcome the loss of Silva and St-Pierre in similar fashion, though new stars will have to emerge.
"I'm a big fan [of Silva's] and I have been since he came here," White said. "It's one of those crazy things. In a million years, you never expect to see that. This will be a tough thing to overcome and come back from at his age. He literally left here and is going straight into surgery. … Anderson Silva has been amazing, and is one of the greatest of all-time, if not the best ever. It's a [expletive] way to see him go out, but it's part of the game."
No one ever likes to see anyone leave with a gruesome injury, but it's particularly difficult to see a great like Silva go out that way. He had so many of the UFC's finest moments, but his career will now be remembered as much for how it ended as for what he accomplished.
That, though, is sport, and it's the hard reality the fighters live.
The end can come at any moment, in a fight and in a career, and it seemingly did just that Saturday for Anderson Silva.