Melbourne, Australia, 27 January 2013 | AAP

Victoria Azarenka broke down in tears after retaining her Australian Open crown and world No.1 ranking with a drama-charged final triumph over Chinese challenger Li Na.

In an extraordinary encounter, Li needed two separate medical timeouts and was treated for possible concussion before finally succumbing 4-6 6-4 6-3 to the top seed after two hours and 40 suspense-filled minutes on Saturday night.

Li had hundreds of millions of Chinese hearts in mouths for the first time when she collapsed in a heap during the second set and hobbled off court.

She returned, though, six minutes later with her left ankle strapped and recovered from a service break down to draw level at 4-4 and close to within two games of taking the title.

Li looked for a second time like she may have to retire after falling heavily and hitting her head on the Melbourne Park centre court on the very first point after the resumption from a nine-minute break for the Australia Day fireworks.

Li was cleared after medical testing from tournament doctors and conjured a break point while leading 2-1 in the deciding set, only for Azarenka to rally and deny the 2011 French Open champion a place in the history books as the oldest woman to win the Open singles crown.

Had Azarenka lost, the Belarusian would also have relinquished her top ranking to Serena Williams, the reigning Wimbledon, US Open and Olympic champion.

Instead, she joins Williams (17), Venus Williams (7), Maria Sharapova (4) and Svetlana Kuznetsova (2) as the only active players with multiple Grand Slam titles.

The 23-year-old was roundly condemned for taking a controversial double medical timeout immediately after blowing five match points in her semifinal victory over American teenager Sloane Stephens.

The Belarusian had the last laugh though, collecting the winner’s cheque for a record $2.43 million after seeing off Li in a tense rollercoaster ride lasting almost two-and-three-quarter hours.

Azarenka said the tears were “a bunch of everything”.

“It was emotion, relief, joy, everything,” she said.

“You never know how you’re going to react and it just comes from the bottom of your heart.

“It’s definitely been really tough for me these whole two weeks, and very emotional.

“Everyone knows now that I’m an emotional player and it just proved that.”

Azarenka again apologised for her untimely medical timeout against Stephens.

“But there’s things you can’t take back,” she said.

“There were new experiences for me over the past two days. I’m glad I have been able to turn things around.”

Li, turning 31 next month, had been bidding to remove Australian great Margaret Smith Court from a page in the Open record books as the oldest woman to reign in the 45-year open era.

Alas, lightning struck twice for the Chinese tennis pioneer who two years ago became her country’s first and only major singles champion with a breakthrough success at Roland Garros.

Entering Saturday night’s final, Li was the only player in the past 25 Grand Slam women’s deciders to squander a one-set lead.

That defeat came against Kim Clijsters at Melbourne Park in 2011.

Now it has happened again in a final full of twists and turns.

But she vowed to return to try again.

“I know I’m not young, but I have to say I’m very [much] looking forward to next year,” Li said.

Drama and tension aside, the match featured 16 service breaks and 77 unforced errors in 29 games.