The Bucks announced Portis’ injuries on Wednesday and said he would be reevaluated in two weeks.
Portis, who turns 28 on Feb. 10, is averaging 14.4 points and a career-high 10.1 rebounds per game. The 6-foot-11 forward will miss a game for the first time this season when the Bucks host the Denver nuggets Wednesday night.
He was injured the same night as the double MVP Giannis Antetokounmpo and three-time All-Star Kris Middleton is coming back from knee injuries. Middleton, who suffered a right knee injury, played only his eighth game of the season on Monday. Antetokounmpo returned after missing five games with left knee pain.
Portis missed almost seven weeks when he sprained the MCL while with the Chicago Bulls in 2018-19.
The Associated Press contributed to this report.