Widely tipped to leave the Power and return to Victoria at the end of the year, Butters was hurt in a 14-point loss to St Kilda at Marvel Stadium on Saturday.
Mitch Georgiades (concussion), Lachie Jones (ribs) and Jack Lukosius (calf) were also injured, and Jason Horne-Francis was handed a one-week suspension for rough conduct.
The weekend of carnage leaves Port short-handed for a home clash with ladder leaders Fremantle at Adelaide Oval on Saturday.
Butters, who will have surgery in the coming days, hasn't yet been ruled out of returning in the latter stages of the campaign.
"The midfielder's timeline will become clearer following the repair, but he is expected to miss at least four weeks," a Power statement said.
Jones was cleared of serious internal damage after a heavy knock to the ribs, with he and Lukosius both set to be assessed ahead of the Fremantle clash.
Match review officer Michael Christian gave Horne-Francis a one-match ban for his high bump on St Kilda defender Liam Stocker.
The incident was graded as careless, medium impact and high contact.
The Power (6-11) sit 15th in Josh Carr's first season as coach after he took over from the long-serving Ken Hinkley.
9°C