The 22-year-old Chiefs backrower made his All Blacks debut against Fiji last year and went on to become a first team regular in a season which was capped with the World Rugby accolade.
He sustained a knee injury on New Zealand's November tour to Japan, England, Ireland and France and Friday's surgery will reveal more about the extent of the problem.
"The fact that he's got to have surgery gives you an indication that it's reasonably serious," Clayton McMillan, Sititi's coach at the Hamilton-based Chiefs, said.
"But we don't know how serious at this stage. He's able to walk around, so it's one of those little niggles that you never really truly know the extent of until you get under the surgeon's knife and they can give some clarity to that."
McMillan said Sititi would be a "huge loss" if he was out for a long period.
"Everyone's seen how he's played over the last 12 months and it's never nice to lose players of that calibre," he said.
"He generates a lot of excitement for his ability.
"We'll miss him and all we can do is jump in behind the young man and help with his rehab, however long that takes, and get him back out on the field as quickly as possible."
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