US Olympic gold medal snowboarder Chloe Kim's Milan-Cortina hopes in doubt after shocking injury

U.S. Winter Olympics star snowboarder Chloe Kim's hopes for a gold medal three-peat are in serious doubt after she suffered a surprising shoulder injury. 

Kim said Thursday that she took "the silliest fall" in training, which caused her to dislocate her shoulder, threatening her chance to win a third straight gold medal at the Milan-Cortina Winter Olympics in February. 

Kim posted video of the accident in Laax, Switzerland, earlier this week as she practiced for a key Olympic tune-up there next weekend.