Silvestre de Sousa was taken to Addenbrooke’s Hospital in Cambridge following a fall at Chelmsford on Friday evening.
The champion jockey was unshipped from Alnadir, trained by Simon Crisford, on the home turn when squeezed for room in a five-runner handicap over 10 furlongs won by Secret Art.
De Sousa was helped to the ambulance, holding his arm.
“We thinking it’s his collarbone but we don’t know,” said his agent, Shelley Dwyer.
“He’s conscious but obviously groggy and very sore.”
Apprentice jockey Theodore Ladd, who partnered runner-up Michele Strogoff, was given a 10-day ban for careless riding.