The series is level at 2-2.
Antetokounmpo hyperextended his knee in the third quarter and spent minutes on the court before being helped into the locker room.
The Bucks were down 62-52 as the two-time MVP left the court, with the Trae Young-less Atlanta pushing on for the win.
Young was ruled out less than an hour before the game began, and Lou Williams led an even scoring attack for Atlanta with 21, while three other starters finished in double digits.
Antetokounmpo was cold in the first half, scoring only six points before more than doubling that tally early in the third until he fell awkwardly contesting an alley-oop.