The Canadian, who returned to competition in May after taking two years off following the 2012 Olympics, was gearing up for her first world championships since 2011 when she fell during a practice session on Wednesday at the worlds in Daytona Beach, Fla., and fractured her left ankle.
“Karen was doing her optional routine and came down off the trampoline bed and with both feet on the frame pad,” said Canadian team manager Eran Silberg.
Cockburn, a bronze medallist at the 2000 Olympics and a silver medallist in 2004 and '08, flew home to Toronto and was expected to have surgery later Thursday or Friday.
The Canadian team, already reeling from the loss of eight-time national men’s champion Jason Burnett, who underwent knee surgery just over a week ago, was dealt another blow Thursday when rising star Samantha Sendel of Aurora, Ont., withdrew from the women’s individual event.
Sendel, who sustained a concussion several weeks ago, had been experiencing dizziness while training this week and was pulled from the individual event.
Sendel finished fifth at last year's world championships.
The loss of Cockburn and Sendel leaves Canada with just two entries in the women’s individual event, with 2012 Olympic champion Rosie MacLennan of Toronto aiming for a second straight world title and Samantha Smith of Kelowna, B.C., looking to qualify for her first world championship final