EDEN PRAIRIE, Minn.  — The Vikings’ seemingly constant search for long-term success and stability at quarterback took another turn on Wednesday.

Sam Bradford’s future was cast in further doubt because of another knee surgery.

And Teddy Bridgewater finally made his way back to the active roster from his devastating knee injury.

Meanwhile, coach Mike Zimmer announced Case Keenum will make his seventh start of the season for the game at Washington on Sunday.

“Case has done great,” Zimmer said. “So we just keep going from there and see how this thing plays out.”

The Vikings (6-2) activated Bridgewater from the physically unable to perform list, adding him to the active roster for the first time in more than 14 months since his left knee was dislocated during practice. The freak injury resulted in ligament tears and an ambulance ride to the emergency room to save his leg.

The Vikings faced a deadline on Wednesday at the end of the three-week window that opened when Bridgewater resumed practice with the team.

To make room on the 53-man roster, Bradford was placed on injured reserve after having arthroscopic surgery the day before on his left knee, which had ACL tears in 2013 and 2014.

Zimmer said “no one knows” when asked if Bradford will play again.

“When they went in there, they just cleaned it out,” Zimmer said. “It’s not bone on bone. There’s a lot of good things, but who knows? We didn’t expect it would be this long.”

Bradford, who will be an unrestricted free agent at the end of the season, led Minnesota to a victory in the season opener over New Orleans by completing 84.3 percent of his passes for 346 yards and three touchdowns.

However, he injured the knee during the game and woke up in pain the next day. He played only one half of one game since then, on Oct. 9 at Chicago when he hobbled around and took four sacks before Keenum came back in to lead the Vikings to a victory.