The Oilers announced Monday that Kelfbom would have surgery.
"He had a chance to see our doctors, we had a good assessment and how we can have a plan going forward with him," Oilers general manager Steve Tambellini told the team's website. "If there's a point in the year where this is going to happen, I guess it's better (to happen) now because we know that he's going to have time to prepare and be ready when it counts next season."
Klefbom, the No. 19 pick in the 2011 NHL Draft, was injured Oct. 9 bracing himself after a collision along the boards in a game against Vaxjo. Due to bleeding around the muscle, he had been in a sling since then before seeing Edmonton's doctors over the weekend.
"I lost my balance after the hit, tried to recover and fell," Klefbom told the website. "It happens, unfortunately. That's hockey."
The 19-year-old had three assists and a plus-7 rating in 11 games with Farjestad this season.
With surgery scheduled for Dec. 13, Klefbom is expected to be sidelined six months.
"It's frustrating, of course. But I'll try to come back even stronger in the summer," he said. "I'm trying to be positive and keep my head high."
The 6-foot-3, 201-pound defender should be ready to compete for a role along Edmonton's blue line in 2013-14. He was the second player selected by the Oilers in the first round in 2011 -- Ryan Nugent-Hopkins was chosen No. 1.
"Once we get the total game plan from the surgery to rehab and the on-ice program, we'll see," Tambellini said of Klefbom's chance to start the 2013-14 season. "I don't think there's any doubt in anyone's mind that he can't come back even stronger than what he is now."