Two others in the $40,000 claiming race for fillies and mares going 1 1/16 miles on Cushion Track -- Mudder of Pearl, ridden by Martin Pedroza, and No Tip For You, piloted by Martin Garcia -- tripped over the fallen horse and lost their riders.
Garcia and Bisono were taken to nearby Centinela Medical Center for x-rays, but were released. Garcia sustained a sprained left wrist and Bisono had a sprained right ankle, according to the Hollywood Park publicity office. Pedroza was examined at the track's first aid facility and released. He did not ride his remaining mount on the card.
Royal Change was euthanized. Mudder of Pearl and No Tip For You walked from the track.
The start of the fifth race was delayed nearly 15 minutes while officials waited for an ambulance to return to the track from the hospital.