Celtics big man Robert Williams has undergone an arthroscopic procedure to remove loose bodies from his left knee and to address swelling in that knee, the team announced today (Twitter link). While the surgery had been expected, the Celtics revealed that the recovery timeline will be longer than initially anticipated. According to the club, Williams is expected to resume basketball activities in approximately eight-to-12 weeks. ESPN’s Adrian Wojnarowski previously estimated a four-to-six week timetable. Williams enjoyed a breakout season in 2021/22, establishing new career highs in PPG (10.0), RPG (9.6), BPG (2.2), games played and started (61), field goal percentage…