ESPN's Adrian Wojnarowski reported the news Monday, noting the LSU product underwent left knee surgery to remove a loose body. The surgery took place in Philadelphia and away from the NBA's campus-like environment at Walt Disney World Resort, and Simmons will remain there for rehab and is expected to be out for the rest of the campaign.
This comes after Shams Charania of The Athletic and Stadium reported on Thursday "treatment options are currently being considered" after the injury was diagnosed as a subluxation of the left patella.
Philadelphia is dealing with injuries to its two biggest stars, as Wojnarowski reported Joel Embiid will miss Tuesday's game against the Phoenix Suns with an ankle injury even though there remains "optimism" it isn't a serious setback.
Simmons, who was sidelined throughout his entire first season in the league in 2016-17 with a foot injury, missed time with back and nerve injuries before the season was suspended in March.
He averaged 16.4 points, 8.0 assists, 7.8 rebounds and 2.1 steals per game while shooting 58.0 percent from the field in 2019-20.
While the 76ers can turn toward Shake Milton in a ball-handling role and pieces such as Alec Burks, Glenn Robinson III and Mike Scott off the bench, it is difficult to envision them living up to expectations and challenging the top teams in the Eastern Conference come playoff time with Simmons sidelined.
The two-time All-Star is both a theoretical building block for the future at 24 years old and someone who can take over a game with his passing, ability to attack the basket and defensive prowess.