LAS VEGAS >> Chris Weidman accepted his UFC middleweight title belt with a grimace and a furtive look over his shoulder. Anderson Silva writhed and screamed on the canvas behind him, his left leg grotesquely broken by a kick to Weidman’s knee.

The champ couldn’t celebrate after the UFC’s year-end show ended with a stark reminder of the brutality at the core of this flashy, fast-growing sport.

Weidman defended his title when Silva broke his shin on a kick to Weidman’s knee in the second round Saturday night, ending UFC 168 with a horrific injury.

While Weidman (11-0) awkwardly acknowledged his victory, the MGM Grand Garden crowd watched with reverence and horror as medical personnel tended to Silva (33-6), whose shin bent to a 90-degree angle after Weidman blocked his kick 1:16 into the round.

"There’s no real excitement in a fight finishing like that, because you never want to see anyone get hurt like that," Weidman said after his second straight win over the long-reigning champion.

Weidman, who earned his belt with an upset victory in July, also dominated the first round of the rematch, pinning Silva to the mat and punishing him with blows. In the second, Weidman used his knee to stop Silva’s kick with perfect mixed martial arts technique, never anticipating the result.

"I did work on checking kicks," Weidman said. "I figured if I (caught) him on my knee, it could really hurt him. Crazy how this happened."

Ronda Rousey also retained her bantamweight title on arguably the UFC’s most anticipated show of the year, submitting Miesha Tate with a third-round arm bar. Rousey then walked away from her bitter rival’s offer of a post-fight handshake, earning ferocious boos from the Vegas fight crowd.

But Rousey’s questionable sportsmanship was dwarfed by the unquestionably awful finish to the main event.

Although the injury happened too quickly to be seen by most naked eyes in Las Vegas, the sound of Silva’s cracking shin could be heard at cageside. Thousands of fans cringed and moaned when the replay was shown on the arena’s big screens.

"I knew coming into the fight that what he could hurt me most with was the leg kicks," Weidman said. "We trained checking the kick a lot. The idea is to pull your leg and for their shin to land at the knee. That’s exactly what I did, and I felt his leg go right away."

Referee Herb Dean waved off the fight when Silva fell back, clutching his leg with both hands. Silva left the octagon strapped to a stretcher with a brace on his leg, screaming in pain.

With his belt back around his waist, Weidman paid tribute to the injured ex-champion.

"He’s still known as the greatest fighter of all time," Weidman said.

Silva’s nearly seven-year reign atop the middleweight division ended nearly six months ago when Weidman stopped the preening, posturing champion with a left hook at UFC 162.

With two straight wins, the former Hofstra wrestler has firmly ended Silva’s reign. The injury in the rematch conceivably could end the 38-year-old Brazilian’s MMA career.

The show was heavy on violent finishes. Heavyweight Travis Browne knocked out veteran Josh Barnett in the first round with a series of elbows to the head, earning the third straight early stoppage on the pay-per-view portion of the card.

Before the unsettling main event, Rousey (8-0) got the biggest test of her ascendant career.

Rousey had never seen the second round of an MMA fight, but Tate tested the champion with striking and tenacity. Although Rousey repeatedly tossed Tate (13-5) to the canvas and pounded on her, Rousey couldn’t finish until getting her weary opponent into her patented arm bar — the submission move she has used to end each of her eight professional fights.

"I respect Miesha very much as a competitor," said Rousey, who feels Tate insulted her family. "But I can’t respect a fighter who did what she did, and I cannot shake her hand because of it."

Tate landed plenty of strikes to Rousey’s head, particularly during a thrilling first round in which she tested Rousey’s chin. Rousey gradually wore down Tate and finally finished her, violently bending her elbow and forcing Tate to tap out.

"Going more than one round was a good experience," Rousey said. "I needed that experience in the octagon, and as my mom said, better to get it in a win than in a loss."

But when Tate attempted to shake her hand, Rousey slowly rose and walked away. The crowd booed vociferously when the replay of the snub was shown in slow motion, but Rousey didn’t apologize.

Nearly two years ago, Rousey defeated Tate by first-round arm bar to claim Tate’s Strikeforce title, cementing her meteoric rise from the U.S. Olympic judo team to the apex of MMA. Rousey and Tate have made no secret of their distaste since that bout, further stoked by their combative appearance as coaches on the most recent season of "The Ultimate Fighter," the UFC’s competition reality show.

"In judo, I didn’t know what a cheer was," Rousey said. "Cheers are what’s new."