Three female riders were taken to hospital after falls at the Badminton Horse Trials on Sunday.
Elizabeth Power, the sister of Grand National-winning jockey Robbie, was initially unsonscious after coming down from her mount Kilpatrick River during the cross-country event.
She was airlifted to Frenchay Hospital in Bristol, where her condition is described as "stable".
Compatriot Camilla Spiers and German Ingrid Klimke also went to Frenchay.
Speirs, riding Portersize Just A Jiff, fell at the L200 Pick Ups while Klimke tumbled off FRH Butts Abraxxas entering Huntsmans Close, a fall that left her requiring knee x-rays.
Action at the event was briefly halted while Elizabeth Power was treated after parting company at the Sunken Lane.
The 26-year-old and Robbie, who won the National Aintree on Silver Birch in 2007, are children of top showjumper Con and former eventer Margaret Power.
She lives in County Meath but spends the eventing competition season based at Marlborough, Wiltshire.
Kilpatrick River, a 13-year-old former racehorse who was unhurt in the drama, finished 11th with Elizabeth Power on their Badminton debut in 2009.
Veteran Mark Todd, on NZB Land Vision, leads going into the final day at Badminton.
The 55-year-old double Olympic champion will become the event's oldest winner if he triumphs in Monday's showjumping finale.