Graham Lee is likely to miss both the Cheltenham Festival and the John Smith's Grand National after dislocating his hip in a fall at Southwell on Wednesday.
The former Grand National winner Lee was hurt when he was unseated from the Ferdy Murphy-trained Rich Lord at the fourth fence in the Win Whatever The Result With BetAngel Handicap Chase.
He was immediately taken to the Queen's Medical Centre in Nottingham where he was told he had suffered a suspected fracture to his right femur, an injury that will require surgery.
"He's not had an x-ray yet but it looks like a fracture to his right femur. He'll have his hip and pelvis checked out too as it is high up on his leg," Doctor Alison Green reported.
"He will require surgery either way and I would think he'll be back in the saddle between three and six months."
However, an X-ray revealed that he had in fact suffered a hip injury that is likely to keep him sidelined for the rest of the season.
"I was spoken to Becky, Graham's wife, and he has just come out of theatre," Lee's agent Richard Hale said.
"The hip was definitely dislocated and has been put back in. As to whether he requires surgery, that has yet to be confirmed.
"I would say an injury like that could mean the end of his season."