Robert Havlin is is set to miss the start of the Flat season at Doncaster on March 30 as he recovers from the injuries suffered in a fall at Kempton last month.
The jockey is targeting the first week in April for his return from the multiple injuries he suffered in the fall from the fatally injured Beehaar on February 5.
Havlin broke his collarbone and fractured some ribs after his mount collided with another horse on the home turn in a mile handicap. After spending a few days in hospital in London, Havlin has since been making progress at his Newmarket home.
He said on Monday: "I've had some scans recently and the doctors were happy with them, but they did discover I've torn a cruciate ligament in my knee.
"My ribs are still a bit sore and it will take a few more weeks. I don't want to come back and ride a horse who pulls as that may set my ribs back. The doctors are pleased with my collarbone and I'd hope to be back in the first week in April."
The rider added: "I've been having regular physio and went on the bike yesterday, which was a help, but it will be great when they get Sir Peter O'Sullevan House opened at the British Racing School in Newmarket, where they will have all the kit.
"I had thought about going to Oaksey House in Lambourn but it's far enough away."
Long attached to the John Gosden yard, Havlin was lying fourth in the all-weather jockeys' championship with 36 winners at the time of his fall.
The 45-year-old enjoyed his best season in 2018 with 127 winners.