It was their 12th straight win and maybe their very best of the 2012-13 season. The Knicks achieved a 50-win season yesterday and further validated the streak by quieting Oklahoma City’s raucous Chesapeake Energy Arena and muting Kevin Durant with a 125-120 shootout victory on national TV. A ferocious Carmelo Anthony outplayed Durant and trusty sidekick J.R. Smith hit two daggers in the final 1:30 to put it away as the Knicks made a major statement to critics who question whether they are a legit title contender. “A lot of people said we were going to lose this game,’’ Raymond Felton said. “That’s a great win. A great win against a great team in this building.” In moving to 50-26, the Knicks have their first 50-win season since 1999-2000. Their magic number to clinching their first Atlantic Division crown since 1993-94 is one. Anthony finished with 36 points and 12 rebounds to Durant’s 27 and three. Anthony’s franchise-record-tying streak of three straight 40-plus games ended, but that hardly mattered. “One of the biggest wins we’ve had in a long time,” Anthony said. “To come out here, keep our composure, it’s a tough place to win.’’ The Knicks can clinch the division crown tomorrow vs. Washington. They have now beaten both Miami and OKC during the streak, though the Heat didn’t play LeBron James and Dwyane Wade.