Jockeys Jim Crowley, Trevor Whelan and David Noonan will require "prolonged recovery and rehabilitation" after their falls, the Injured Jockeys' Fund has said.
Racing was delayed for nearly half an hour at York on Sunday after Crowley and Whelan were injured in the Garrowby Stakes.
Meanwhile Noonan was kicked by a horse at the start of a race at Fontwell.
The IJF confirmed Crowley and Whelan were taken to Leeds General Infirmary after their falls.
"Jim sustained a pelvic and leg fracture and after initial treatment to stop internal bleeding on Sunday, he had surgery on Monday to stabilise his fractures," a IJF statement read.
"He is doing well post-operation, is in good spirits and will remain in hospital for the time being."
The IJF said Whelan is scheduled to see a specialist ankle surgeon on Tuesday after suffering a "complex ankle fracture".
Crowley was riding the William Haggas-trained race favourite Almeraq when, short of room about a furlong out, his mount clipped heels with another horse and came down.
Almeraq rolled over Crowley while Henry Candy's Tiger Bay following behind had nowhere to go and was brought down, which also sent Whelan to the turf.
Both horses appeared to escape without serious injury.
Noonan had surgery at Royal Sussex County Hospital on Monday to stabilise a leg fracture and the IJF said he "hopes to be discharged soon".
"All three jockeys will require prolonged recovery and rehabilitation," the injured jockeys' body added.
"They are extremely grateful for the excellent care they received from the medical teams on the racecourses and would like to thank everybody for their concern."