Dan Henderson, top, punches Mauricio Rua during the second round...

Dan Henderson, top, punches Mauricio Rua during the second round of a light heavyweight bout at UFC 139 in San Jose, Calif. Henderson won by unanimous decision. (Nov. 19, 2011) Credit: AP

A knee injury forced Dan Henderson to pull out of the main event at UFC 151 just nine days before he was to challenge for Jon Jones' title in Las Vegas, thus causing the UFC to cancel the entire card.

UFC president Dana White announced the news Thursday afternoon on a conference call. Henderson has a partial tear of the medial collateral ligament in his knee.

"For the first time in 11 years, we're going to cancel an event," White said.

Chael Sonnen was offered Henderson's spot in the main event and accepted it. Jones did not.

"Around 8 or 9 p.m. here, we had a fight," White said. "The one thing I never thought would happen happened. Jon Jones said he won't fight Chael Sonnen on eight days' notice."

On the conference call, White said that Jones didn't take the fight on the advice of his head trainer Greg Jackson.

"Me are Lorenzo are both disgusted" with Jones, White said.

Jones will now fight Lyota Machida at UFC 152 in Toronto on Sept. 22. That card will remain as UFC 152, the company announced after the conference call ended. UFC 151 will be just not exist.

White said he was unsure what will happen to the other fighters on the the Sept. 1 card, but "we'll figure it out."

"Good for you Jon Jones, you've made a lot of money," White said. "There's a bunch of guys on the undercard that this is how they pay their family.

Tickets to the fight at Mandalay Bay Events Center will be refunded, White said.

"The first fight ever canceled in UFC history since we've owned the company and the first champion to ever turn down a match," White said.

Rumors began circulating on Twitter last Wednesday night that Henderson was hurt during training and would have to pull out of the fight.

Then, at 12:07 a.m. ET, this tweet came from Henderson's verified Twitter account: "Just got done with a great training session with the boys. @CyrilleDiabate @tarecfighter @heathlsims @RFBJJ @rockholdMMA."

Roughly 26 minutes later, Henderson tweeted "Headed to the house to get worked on by @msmariahv to finish of the day happy."

With nine days until the main event against one of the UFC's biggest stars, Henderson's injury left the UFC scrambling for a new headliner to carry the pay-per-view card at the Mandalay Bay Events Center in Las Vegas. Jay Hieron, a Freeport native, and Jake Ellenberger was the co-main event, but it's hard to see that fight becoming the promotable main event.

After a second defeat to middleweight champion Anderson Silva in July, Sonnen announced he would move up to light heavyweight. He is supposed to fight Forrest Griffin in December, and as a Team Quest teammate of Henderson, Sonnen has been outspoken lately about Jones.

Recently, Jones has been critical of a rematch with Machida, whom he beat by second-round submission last December. Jones said he didn't see that fight as a big PPV buy generator.

"If I get a call today that he doesn't want to fight Machida, we'll have another conference call later today," an angered White said.

Henderson, 41, is coming off perhaps the best win streak of his career, with wins over Mauricio "Shogun" Rua, Fedor Emelianenko and Rafael "Feijao" Cavalcante. His last bout, at UFC 139 against Rua, was an epic five-round battle that many considered among the greatest MMA fights ever.

"I appreciate the loyal support that I have felt from my fans," Henderon wrote on his Facebook page. "I want to thank all of my coaches and team of guys for the great support with my training camp. Most importantly, I appreciate their honesty when I needed them the most to make this very difficult decision. I also want to thank Dana and Lorenzo for being so understanding and supportive."

The lasting impact of the UFC's first cancelation of a card won't be known for some time. In the short term, however, there is the loss of production and marketing money for the company not to mention the PR hit. And then there's the financial impact of fans' flights to Las Vegas, cancelation and change fees and the loss of hotel revenue.

"It's a major, major deal," White said about canceling the card. "We lose [a lot] of money."

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