Gov. Tim Walz is scheduled to undergo knee surgery Thursday, a procedure that will require Lt. Gov. Peggy Flanagan to briefly assume the state's top job.

Walz will have surgery for a medial meniscus tear in his left knee, and will need another surgery soon for a similar tear in his right knee, his office announced Monday.

He heads in to surgery at 12:30 p.m. Thursday and will be under a general anesthetic. He will transfer his office's responsibilities to Flanagan during the procedure.

"Although I am confident in my full and speedy recovery, I believe it is appropriate to exercise diligence and follow the appropriate processes prescribed in law," Walz wrote in a letter he sent Monday to the House speaker and Senate president, notifying them of the upcoming transfer of power.

He stated in the letter that he would send another written declaration to the ­legislative leaders when he is able to resume the job.

The temporary transfer of power to the lieutenant governor did not occur under the previous administration. Former Gov. Mark Dayton, who underwent a series of back surgeries while in office, was also under general anesthesia for those procedures. But he did not relinquish his responsibilities during surgery.

The Minnesota constitution says the lieutenant governor shall be governor "in case a vacancy occurs from any cause whatever in the office of governor." It does not specify what length of time qualifies as a vacancy.

Walz expects to be back in his office Monday and recover his full physical capacity in less than six weeks after some physical therapy, according to a news release from the governor's office. The governor, who is a runner, noticed pain in his knees while he was on the campaign trail.

"After years of running, this minor surgery will help ensure I can hit the pavement again soon," Walz said in the release. "I expect a smooth surgery and I have full confidence in Lieutenant Governor Flanagan to temporarily hold the power of the office while I am under anesthesia."