Mixon is expected to be sidelined for two to four weeks, the NFL Network reported, citing a source.
The second-year running back was injured in Thursday night’s 34-23 victory over the Baltimore Ravens. Mixon left the game in the first half but returned in the fourth quarter.
Mixon finished with 84 yards rushing on 21 carries as Cincinnati posted its second straight 34-23 victory. He ran for 95 yards on 17 carries in a season-opening win over Indianapolis.
Following Thursday’s game, Mixon told reporters he would have not returned to the lineup if the Bengals held a bigger lead.
“I had to talk myself to going back in,” Mixon said. “It’s mental toughness. It was real hard. … It felt weird. The knee was hurting. The mental side of it is you always want to play 100 percent. When it’s bothering you, it’s hard mentally. I just had to check back in mentally and tough it out physically.”
The 6-1, 228-pound Mixon was selected by the Bengals in the second round (No. 48 overall) of the 2017 draft out of Oklahoma and rushed for 626 yards and four touchdowns in addition to catching 30 passes for 287 yards as a rookie.
Giovani Bernard is expected to take over as the starter in Mixon’s absence. Bernard has rushed for only 25 yards on seven carries in the first two games but he has been a reliable two-way threat throughout his tenure with the Bengals.
A second-round in the 2013 NFL Draft, Bernard rushed for at least 680 yards in each of his first three seasons. He had 458 yards and two rushing touchdowns in 2017.
Bernard also is a dangerous pass receiver, collecting at least 39 catches in each of his five seasons, including a career-best 56 at a rookie.