Bucks superstar Antetokounmpo left the game in Chicago in the second quarter shortly after a heavy collision with a stanchion as he chased down a block.
An initial injury report from the Bucks said Antetokounmpo had suffered a sprained right wrist.
The injury came in the final round of NBA regular season fixtures before this week's All-Star weekend.
Antetokounmpo is due to captain the Eastern Conference line-up in Sunday's All-Star Game against the LeBron James-led Western Conference.
A significant injury to Antetokounmpo would be another body blow to the mid-season NBA showpiece, which is already missing Golden State superstar Steph Curry and the Phoenix Suns' Kevin Durant.
Antetokounmpo's injury took the shine off another polished performance by Milwaukee, who are second in the Eastern Conference behind leaders Boston with a 42-17 record.
With Antetokounmpo making an early exit, it was left to Milwaukee's Brook Lopez to provide the offensive thrust for the Bucks.
Lopez finished with 33 points, seven rebounds and two assists while Jevon Carter impressed with 22 points, six rebounds and six assists.
The defeat was another setback for Chicago however.
The Bulls have now lost six straight games and have fallen outside the play-in places in the Eastern Conference at 26-33.
The Bulls' offence was blunted by the injury absence of DeMar DeRozan, who also missed Wednesday's game against the Indiana Pacers with a thigh injury.
It is not clear if DeRozan will be fit to play in the All-Star game, where he is among the Eastern Conference reserves.
In DeRozan's absence, Nikola Vucevic led the Chicago scoring with 22 points and 16 rebounds while Zach LaVine finished with 18 points.
In Thursday's other early game, the Washington Wizards staged a dramatic late fightback to stun the Minnesota Timberwolves 114-106 on the road.
The Wizards' Bradley Beal scored 30-plus points for the third time in four games, finishing with 35 points, six rebounds and five assists.
The Timberwolves led by 20 points in the first quarter and looked on course for victory after leading by 18 points with just over two minutes remaining in the third quarter.
But Washington outscored Minnesota 38-19 in the fourth quarter to take the lead for the first time and close out victory.
Anthony Edwards was the pick of the Minnesota offence with 34 points while Kyle Anderson added 18 and Rudy Gobert 17.
In the late game, the Los Angeles Clippers beat the Phoenix Suns 116-107, with Phoenix guard Chris Paul surpassing Michael Jordan for third on the NBA's all-time steals list.
Paul now has 2515 steals, averaging 2.1 steals per game over his 18-year NBA career.
