A league source told The Boston Globe that Welker will undergo the procedure next Tuesday at Massachusetts General Hospital.
Welker tore both the medial collateral ligament and anterior cruciate ligament in his left knee making a cut after catching a pass. The MCL did not need surgery, so he let that heal before having a procedure on the ACL.
"We're just taking our time right now," Welker told Jim Traber during a radio interview in Oklahoma City, Welker's hometown, last week. "That's one thing -- we've got a little bit of time right now to wait on that to heal and just kind of get ready and make sure that we exhaust all the options and find out the best one for myself to give me the best chance to get back out there on the field."
The Globe reported that waiting for the MCL to heal helps prevent infection. Pats quarterback Tom Brady suffered from infections in his knee after getting injured early last season.
Welker could miss anywhere from six to 12 months, depending on what doctors find.
In his third season with New England, Welker set a franchise record with 123 catches on the season. He had 1,348 yards and four touchdowns. Without him, the Patriots lost 33-14 to Baltimore in an AFC wild-card game.