Ben Simmons' NBA season is in doubt after confirmation the Australian star suffered a partially dislocated kneecap in the Philadelphia 76ers' win over the Washington Wizards on Wednesday.

The team announced the news the day after Simmons limped off court in his third game for the Sixers since the NBA's season restart.

Doctors have not yet determined how long Simmons will be sidelined. He has been listed as day-to-day on the injury report.

An initial MRI test came back negative. Treatment options are still being considered.

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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 was feeling anxiety over the situation.

"There is clearly disappointment," Brown told reporters.

"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 … is obviously there.

"But he's a great teammate, and his teammates care about him."

Simmons had pinched a nerve in his back before the season was originally suspended on March 11.

Brown had previously said the lengthy season break due to COVID-19 gave the Australian time to get back to full fitness.

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The two-time All-Star got hurt midway through the third quarter against the Wizards.

Simmons sustained the injury either while grabbing a rebound, or immediately thereafter.

He dribbled slowly up the floor and passed the ball to teammate Al Horford.

After a whistle stopped play with 5:46 remaining, Simmons began touching his knee and walked off the court, continuing through to the locker room.

He was shown walking gingerly as he exited the arena in street clothes shortly before the end of Philadelphia's 107-98 win.

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Simmons had eight points, six rebounds and four assists in 23 minutes.

He is averaging 16.4 points, 8.0 assists and 7.8 rebounds in 57 games this season, but only 12.33 points, 4.33 assists and 7.0 rebounds in three games since the restart.

Philadelphia's next game is against the Orlando Magic.

Reuters/ABC