Replay - Semenya wins world title
South African athlete Caster Semenya will miss the Commonwealth Games in India because of a back injury.
The 19-year-old 800 metres runner underwent an MRI scan on Tuesday, which confirmed the back problem.
Semenya had been been expected to challenge for gold at the Games, which run from 3-14 October in Delhi.
The world 800m champion returned to competition in July after 11 months on the sidelines following a series of gender tests.
A statement from the South Africa Sports Confederation and Olympic Committee (Sascoc) said Semenya had told them in the last 48 hours that she had been suffering serious lower back pain and had not been comfortable in her last few races.
It is our medical view that physically and emotionally she would not be capable of doing justice to her talent at an event of this magnitude
Shuaib Manjra, South African team doctor on Semenya
Scans in Johannesburg confirmed the extent of the injury.
South Africa's team doctor Shuaib Manjra said if the athlete made an appearance at Delhi, she risked serious injury blighting her chances at the 2011 Athletics World Championships and London's 2012 Olympics.
Manjra wrote on Sascoc's website: "It would serve no purpose to have an athlete in Delhi who was struggling with any sort of injury that would compromise performance.
"It is our medical view that physically and emotionally she would not be capable of doing justice to her talent at an event of this magnitude."
Earlier on Tuesday, Semenya's coach Michael Seme had assured reporters that she would be competing at the Commonwealth Games.
"She had a slight pain in the back, but the issue has been blown slightly out of proportion," he told the Press Association.
"She's going to be 100% fit. We are training and will be there."
Team South Africa, who have just moved into the athletes' village in Delhi, are waiting on late fitness calls over long jump star Khotso Mokoena and men's 800m world champion Mbulaeni Mulaudzi.
Mulaudzi is also feeling back pain and has undergone a last-minute scan to determine the extent of the problem.
His manager Peet van Zyl said: "With him not having trained for three weeks the outlook does not look good at all."