Philadelphia 76ers All-Star Ben Simmons suffered a partially dislocated left kneecap during Wednesday's game against the Washington Wizards, the team confirmed on Thursday.
Doctors have not yet determined how long the All-Star will be side-lined, with treatment options still being considered.
Asked if Simmons would miss the rest of the season, Philadelphia coach Brett Brown said, "Some of the information is fluid. It's just that the stuff is still being evaluated."
Brown said the 24-year-old Simmons is feeling anxiety over the situation.
"There is clearly disappointment," Brown added. "I don't know if anyone really understood what he did to get ready to play basketball again [after a 2016 foot injury]. He really invested time.
"It's monotonous, some of the smaller things he had to do. ... I think the uncertainty of what really is it right now is obviously there. But he's a great team-mate, and his team-mates care about him."
Simmons got hurt midway through the third quarter. He was shown walking gingerly as he exited the arena shortly before the end of Philadelphia's 107-98 triumph.
He sustained the injury either while grabbing a rebound or immediately thereafter. Simmon dribbled slowly up the floor and passed the ball to team-mate Al Horford. After a whistle stopped play with 5:46 remaining, the Australian began touching his knee and walked off the court and continued to the locker room.
Simmons had eight points, six rebounds and four assists in 23 minutes on Wednesday. He is averaging 16.4 points, 8.0 assists and 7.8 rebounds in 57 games this season.
Philadelphia, who currently occupy sixth in the Eastern Conference standings, next play on Friday against the Orlando Magic.