Mixon took to Instagram on Saturday evening.
The procedure, to remove a small particle in his knee that was dislodged Thursday night, is expected to sideline Mixon for two weeks, a source told ESPN's Adam Schefter.
Doctors who examined Mixon's MRI on Friday believed the particle to be from an old injury, a source told ESPN.
Mixon, who was limping in the locker room after the Bengals' 34-23 victory over the Baltimore Ravens on Thursday, rushed for 84 yards on 21 carries. He admitted that his knee hurt and described the injury as "some weird tweak."
Mixon shuffled in and out of the game because of the injury.
"It felt weird. My knee was hurting," Mixon said. "Other than that, it's just the mental side of it. You always want to play at 100 percent, but when something is bothering you, it's hard mentally. I just had to check back in mentally and physically tough it out."