Medics rushed to the aid of David Probert after his horse kicked him before a race.
The jockey was treated after the 'horrible incident' involving his intended mount Bits and Bobs. Windsor Racecourse staff put up screens while Probert received assistance in the parade ring.
Sky Sports Racing later reported that he was taken to hospital in Slough for further assessment. It is understood he might have suffered a leg injury.
Explaining what happened, presenter Matt Chapman said: "There has been a horrible incident. Imagine a horse kicking out and the sound it makes hitting a plastic railing - in this case it wasn't the railing but a jockey. That was the noise that reverberated around Windsor.
"Before the screens were put up a doctor was with him and he moved his head."
Bits and Bobs was withdrawn from division one of the British Stallion Studs EBF Restricted Maiden Stakes. It went off eight minutes late and was won by Perfect View, a debutant part-owned by music agent Emma Banks.
Chapman added that Probert, who has ridden in 371 races this year, would be accompanied to hospital by his partner.
In 2021, he broke through the £2 million prize money barrier for the first time – and has enjoyed his best two years in the saddle to date. Sandrine, a horse trained by Andrew Balding, like Bits and Bobs, was one of his key winners in last summer's Group 2 Lennox Stakes.
Racing fans took to social media to say they were thinking of Probert.
"Wishing David Probert all the very best. Hoping all is ok," one posted on Twitter.
