Carlos Condit was the most recent fighter to score a flying-knee knockout inside the Octagon, unleashing one against Dong Hyun Kim in July 2011.
The timing and technique required to execute a flying knee make it a difficult move to pull off against elite competition. However, when it does land, the flying knee can led to some of the most devastating knockouts in MMA.
The number of flying-knee knockouts to occur under the UFC banner can be counted on two hands.
Of those spectacular finishes, these are the five best.
After beating Joe Stevenson to become the UFC lightweight champion, BJ Penn's first title defense came against former 155-pound champion Sean Sherk.
Near the end of the third round, Penn timed a flying knee as Sherk rebounded off the cage, magnifying the damage caused by the strike. Left in a heap against the fence, Sherk ate a few more punches before the round came to an end.
Though the horn sounded, Sherk was unable to continue fighting, which gave Penn his first of multiple UFC title defenses.
Riding a five-fight winning streak, Thiago Alves was given an opportunity to fight former UFC welterweight champion Matt Hughes in June 2008. Hughes had lost to Georges St-Pierre in two of his previous three appearances and was hoping to use his wrestling to get back into the win column against Alves.
Though Hughes secured one takedown in the first round, he was stuffed on four other attempts, which did not bode well heading into the second round against a striker like Alves.
Just one minute into the second stanza, Alves blasted Hughes with a flying knee. The UFC legend rolled to his back, and Alves finished the fight with a big right hand.
The first featherweight bout in UFC history did not disappoint.
Moving down from lightweight for his Octagon and 145-pound debut, Pablo Garza picked up Knockout of the Night honors for his win over Fredson Paixao at the TUF 12 finale.
As Paixao dropped levels for a takedown in the opening minute of the bout, Garza leaped upward and landed his left knee to his opponent's face. Paixao folded over and ate one more right hand from Garza before referee Steve Mazzagatti rescued him.
Terry Martin entered his UFC debut with 10 straight wins and only one career loss (against Stephan Bonnar). Welcoming Martin to the Octagon was James Irvin, who had defended the WEC heavyweight title in his previous appearance.
After getting off to a slow start and having trouble with Martin's grappling in the first round, Irvin wasted no time in opening up his striking in the second stanza. Just nine seconds in, Irvin charged forward with a flying knee and kept walking after landing it.
He had left Martin flat on his back and unconscious.
With three Fight of the Night performances throughout his career, it shouldn't be surprising to see Spencer Fisher atop this list of acrobatic and entertaining knockout artists.
At UFC 60, Fisher welcomed Matt Wiman to the Octagon in brutal fashion.
Fisher opened the second round of the fight impressively, landing some solid combinations. After he had his bell rung by a Fisher punch, Wiman wagged his finger in dismissal.
Responding as anyone in his situation would, Fisher flew into the air and drove his left knee into Wiman's skull. Completely sacrificing control of his body in hopes of ending the fight with the strike, Fisher flipped over his opponent and walked off after Wiman crashed to the canvas awkwardly.