Fox was riding Justantenner for Barry Murtagh in the first division of the Double Five Whitburn Handicap Hurdle, when falling at the third flight.
He was taken to Borders General Hospital for further assessment, but has escaped serious injury.
Fox said: "I had to get my head scanned but everything was fine and they let me out last night.
"I'm grand this morning. I've got concussion and won't be able to have a concussion test for at least seven days. Hopefully I'll pass the test no bother next week.
"It could have been a lot worse and hopefully I'll be back in the saddle very shortly."
Fox partnered the Lucinda Russell-trained One For Arthur to glory at Aintree in April and the eight-year-old was favourite to repeat the feat next year, before being ruled for the season with a tendon injury a few days ago.
"It was very disappointing news and it's a big blow," Fox added. "Hopefully we can nurse him back to health and he'll be back next season.
"Lucinda has plenty of nice horses, including a lot of young horses, and hopefully one or two of them aren't too bad. There's plenty to look forward to, hopefully."