I believe you're thinking of Kerri Strug at the 1996 Olympics. She did her first vault and her ankle started to hurt. She did her second vault and landed on one foot because her ankle was severely injured. She helped the U.S.A team earn the gold medal.
Kerri Strug
you can twist your arm and ankle. p.s. i am a gymnast
Kerry Strug in the 1996 Atlanta Olympics. But she didnt land on one foot after her final vault. She landed on two feet but having sprained one ankle earlier, that ankle was immediately lifted off the ground as she saluted the judges and then she collapsed to the ground.
The gold medalist in the Men's Vault event at the Rio 2016 Olympics was Se Gwang Ri.
Denis Abliazin won the silver medal in the Men's Vault event at the Rio 2016 Olympics.
The bronze medal winner in the Men's Vault event at the Rio 2016 Olympics was Kenzo Shirai.
Japan won the bronze medal in the Men's Vault event at the Rio 2016 Olympics.
North Korea won the gold medal in the Men's Vault event at the Rio 2016 Olympics.
The country that won the silver medal in the Men's Vault event at the Rio 2016 Olympics was Russia.
France won the silver medal in the Men's Pole Vault event at the Rio 2016 Olympics.
The bronze medal in the Women's Pole Vault event at the Rio 2016 Olympics went to Eliza McCartney.