Nets general manager Sean Marks announced Friday that Russell had arthroscopic surgery to remove loose bodies from his knee and didn't offer a return timetable, via B/R's Howard Beck.
Russell last played in the Nets' 114-106 loss against the Utah Jazz on Nov. 11. He scored 26 points and grabbed six rebounds in nearly 33 minutes before limping to the locker room late in the fourth quarter.
Acquired in a trade from the Los Angeles Lakers in June, Russell is having the best season of his NBA career. The 21-year-old is averaging career highs with 20.9 points, 5.7 assists and 4.7 rebounds per game.
Leg injuries have been a problem for Russell over the past two seasons. He missed a total of 19 games in 2016-17 with the Lakers, including a two-week absence from Nov. 22 through Dec. 11 after receiving a platelet-rich plasma injection.
The Nets were already thin in the backcourt with Jeremy Lin out for the season after rupturing his patella tendon in the regular-season opener against the Indiana Pacers.
With Russell sidelined for the time being, the Nets have Spencer Dinwiddie and Isaiah Whitehead taking the reins at point guard.