OKLAHOMA CITY (AP) -- Oklahoma City Thunder point guard Russell Westbrook will miss the first 4-6 weeks of the NBA season after undergoing arthroscopic surgery on his right knee Tuesday. General Manager Sam Presti said the three-time All-Star had knee swelling that would not subside, and the procedure was intended to solve the problem. He said doctors determined that a loose stitch was to blame for the swelling, that Westbrook's lateral meniscus has healed properly and the procedure was successful. ''Russell has been incredible in his work and rehabilitation,'' Presti said. ''His performance levels have been tremendous, and he's looked great in the part of practice that he's been cleared to go through. So, we were very, very encouraged in that respect. But when the swelling wasn't subsiding, we made the decision to have the knee evaluated.'' Westbrook also had surgery in May to repair cartilage in his right knee after he was hurt in Game 2 of Oklahoma City's first-round playoff series with Houston. He had had never missed a game in his five NBA seasons before the injury. Westbrook averaged 23.2 points and 7.4 assists per game last season, but he wound up watching the Thunder's second-round playoff exit to Memphis from the bench. Westbrook was hurt on April 24 when Rockets rookie Patrick Beverley lunged for a steal as Westbrook stopped to call a timeout in the second quarter of Game 2. He remained in the game and it wasn't until two days later that the team announced he'd miss the rest of the playoffs. Beverley has said he wasn't trying to hurt anyone and was simply trying to make a play. Last week, Westbrook said once he's fully recovered, he doesn't plan on changing anything about his playing style, including his ability to drive to the basket. Oklahoma City needs offensive help alongside Kevin Durant and Westbrook following the departure of Kevin Martin, who averaged 14 points per game last season. Some of the offense is expected to be picked up by third-year guard Reggie Jackson, who averaged 13.9 points in the playoffs after averaging just 5.3 during the regular season. Also, forward Serge Ibaka returns after averaging 13.2 points per game last season. Presti said losing Westbrook in the early going was worth it for the peace of mind. ''Of course, both from the standpoint we'd like to have him on the floor as soon as possible, but in this case, although we lose a little bit of time, we gained a tremendous amount of confidence in the actual progression and recovery process of the knee itself,'' he said.