Jockey David Harrison was taken to intensive care after his mount My Chief took a heavy fall at Hong Kong's Sha Tin racecourse last night.
The fall happened soon after the start of a six-furlong sprint with My Chief appearing to clip the heels of another runner, unseating Harrison.
At first the injury did not seem too serious as the Welshman appeared to be fully conscious immediately after the fall.
However, on arriving at Sha Tin Prince of Wales Hospital, Harrison was placed in the intensive care unit.
He is expected to undergo X-rays today.
Harrison has enjoyed considerable success since returning to Hong Kong in February, gaining plenty of rides for champion trainer Brian Kan.
During a former spell in the Far East, Harrison partnered Holy Grail to a shock win in the 1999 Hong Kong Derby.
Last year, Harrison won the Irish St Leger at the Curragh and finished fifth in the Melbourne Cup.
PA