* 33-year-old Australian great calls time
* Caps career with six Olympic medals and 11 world titles (Adds quotes, details, byline)
By Ian Ransom
MELBOURNE, Oct 16 (Reuters) - Australia's track cycling queen Anna Meares announced her retirement on Sunday, two months after grabbing her sixth Olympic medal to cap a career defined by courage and sacrifice.
The twice Olympic champion, who won 11 world titles and bore her nation's flag at Rio, mulled bowing out at the 2018 Commonwealth Games in her home state of Queensland but said the physical toll extracted by 22 years of competition had helped make up her mind.
Meares revealed she had taken six cortisone injections in her spine just to get to Rio where she struggled in the defence of her sprint title but took the keirin bronze.
"Having had to change tack for six months leading into it and to achieve the things I have, I feel satisfied and happy to step aside from the sport and try something new and different," the 33-year-old told local broadcaster Channel Nine.
"I have been able to achieve so many wonderful things, more than most. I am the most successful for women in my sport in the field."
A coal miner's daughter raised in a remote Queensland town, Meares spent much of her childhood in the back seat of her parents' car, driving some 250 km to reach the nearest velodrome for training.
She emerged as a 20-year-old sensation in 2004, storming to the 500 metres time trial gold in world record time at the Athens Games, months after winning the world title at her home championships in Melbourne.
Her reputation for toughness was forged four years later, however, when she broke her neck, dislocated her shoulder and tore ligaments in a sickening crash at a World Cup event seven months before the Beijing Olympics.
Wheelchair-bound and with her neck in a brace, Meares told a stunned media conference she intended to compete at Beijing.
Less than two weeks later, she was back on her bike, starting an intensive rehabilitation that would culminate in a sprint silver behind Victoria Pendleton.
Her enthralling rivalry with the British great raised the profile of track cycling, offering a rare narrative of clean competition, even as a seemingly endless string of doping scandals on the men's pro tour blighted the sport overall.
Meares won their dramatic replay of the sprint final at London, the pair's teary embrace after the duel one of the Games' most memorable moments.
A new generation of riders emerged to challenge Meares in the next Olympic cycle, but she remained at the pinnacle in her thirties, clinching her third keirin world title at Yvelines last year.
She said she would remain involved in Australian cycling in mentoring roles, as the national team strives to regroup for Tokyo after a disappointing campaign in Rio.
"It is hard to close this chapter, because it is a bloody big one," she said.
"But I am really excited about the doors opening in to the next chapter of my life." (Reporting by Ian Ransom; Editing by Andrew Both/Amlan Chakraborty)