The 34-year-old Foran sustained the injury on Saturday night in the 26-18 trial win over the Dolphins and scans revealed the worst, as he had expected.
It's anticipated he'll miss 12 weeks and it will be the 18th time in 18 seasons that Foran has gone under the knife.
The Dolphins had mixed news after scans on injuries suffered by Bostock and prop Daniel Saifiti (hamstring) in the Titans trial.
Former Newcastle forward Saifiti is on track to play against South Sydney on March 7 but Bostock, last year's Dally M rookie of the year, will miss the opening two rounds.
"Daniel only came off as a precaution and it is fair to say we didn't risk him because it was only a trial match," Dolphins head of performance Jeremy Hickmans said.
"The injury has settled down nicely and he will aim to train fully next week to get ready to play the Rabbitohs.
"Jack has a low-grade medial ligament injury that will require a few weeks of rehabilitation, so we expect him to miss the first two (NRL) games."
Meanwhile AAP has been told Brisbane have no concerns about the availability of prop Payne Haas (ankle), centre Kotoni Staggs (quad) and fullback Reece Walsh (knee) for round one.
The three stars had minor complaints in the 30-14 win over Canterbury. The Broncos are on a short break but will return to training on Thursday where all three are expected to take part, although their training loads will be managed ahead of their March 6 clash with Sydney Roosters.
In other injury news, Titans forward and 2024 club rookie of the year Josiah Pahulu is undergoing an 11-day recovery protocol after he was concussed at Kayo Stadium after an accidental head clash with Dolphins back-rower Kulikefu Finefeuiaki.
Gold Coast don't play until round two so Pahulu is not in any danger of missing game time.
Foran, who was set to play a No.14 role this year, said he would tackle his rehab with a positive mindset after going through the process so many times before.
He said new halves combination AJ Brimson and Jayden Campbell would do the club proud in his absence.
Foran was impressed with the duo and fellow spine members Sam Verrills (hooker) and Keano Kini (fullback) in Saturday night's trial.
"The way they connected out there, they've been doing it all pre-season and they're just excitement machines," he said.
"You could just see with their style of footy they were able to play off the cuff and they just allowed their natural ability of skill and speed to take over at times which was super impressive.
"They're going to play an instrumental role in the outcome of our season and they're all up for it."
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