Jones Jr. hyperextended his knee during Wednesday's loss to the Brooklyn Nets after landing awkwardly on his leg 36 seconds into the game. He struggled to put much weight on the leg after the fall and had to be helped to the locker room.
While an MRI did not reveal any ligament damage, the Bulls are still losing Jones Jr., who had moved into the starting lineup for the past six games, for an extended absence.
"Everybody got to step up and take on a bigger challenge defensively," Bulls forward DeMar DeRozan said after Wednesday's game. "Understanding and helping each other and kind of using our smarts at the same time."
To help bolster their bench, the Bulls signed forward Malcolm Hill to a 10-day contract on Thursday, a source told ESPN's Adrian Wojnarowski. Hill recently appeared in three games with the Atlanta Hawks during a 10-day deal, including a 13-point, 3-steal performance against the Bulls on Dec. 29.