An American fighter won a UFC bout by disqualification when his Russian opponent threw an illegal knee

• Aljamain Sterling is the first UFC fighter to win a championship via disqualification.
• Petr Yan was withdrawn from the UFC 259 bantamweight match when he landed an illegal knee.
• Watch the rogue knee right here.

American fighter Aljamain Sterling won a UFC bout by disqualification when his Russian opponent Petr Yan threw an illegal knee.

It all went down at UFC 259 inside the Apex, Las Vegas, as the behind-closed-doors mixed martial arts event had been anticipated as the UFC's biggest show for months.

The bantamweight champion Yan put his UFC title on the line against the No.1-contender Sterling in a match on the main card but he was dethroned as a result of his own doing.

Midway through the fight, with Yan ahead on two of the three judges' scorecards, the champion threw a knee when Sterling was already considered down.

Sterling was on the canvas after a failed takedown attempt and despite a warning from the referee, Mark Smith, Yan threw his knee at Sterling.

The 31-year-old was deemed unfit to continue and so he was declared the winner.

Watch the knee strike here:

And aftermath here:

Sterling was declared the winner, the UFC championship changed hands, but the fighter left the title in the Octagon.

"Everything I worked for to this point and to have the fight go like that … I thought the fight was very close, I thought I was down two rounds," said Sterling in a statement sent to Insider.

"That's not the way I wanted to win. That's not the way I envisioned this. I just took the belt off. I was trying to continue even being like that, I was in a bad shape and it would just have been ego taking over and just to get further punishment.

"The ref told me I was down," he said. I don't know. I understand that there is some heat, some bad blood a little bit, but it's all rivalry.

"I wanted to continue," Sterling added. "The fight was fast-paced, it was a lot of action, I know the fans were enjoying that. This was potentially going to be one of the fights of the year or one of the greatest bantamweight fights in history for the title. The action was nonstop until that point."

He finished by saying: "Sorry fans. Sorry that the fight went like this. I hope we get to run it back, do it again and give you the fight you guys deserve."

Yan said at a post-fight press conference that he "didn't mean to do an illegal shot."

According to MMA Junkie, he said: "It sucks, and I think him as a fighter he also don't want to accept the belt this way," Yan said. "And if he's going to be healthy, hopefully we have the rematch soon."

Sterling is the first fighter in UFC history to win a championship by disqualification. With the win, he advanced his pro MMA record to 20 wins (two knockouts, eight submissions, nine decisions, and one other) against three losses.