Votto is getting treatment in Cincinnati and is "as day to day as they come," according to Reds manager Bryan Price.
"He's been out for a while," Price told the Cincinnati Enquirer. "He hasn't seen live pitching. The protocols moving ahead are undecided. It really is a day-to-day process."
Votto is taking ground balls, and the next step would see him take live batting practice.
"He had two things to deal with: Some soreness and the second part is a fairly significant strength deficit in his quad," Price said, according to the Enquirer. "We've gotten most of the pain out of his knee and the limitations that go with that.
"He's really working on strengthening now."
Votto will need clearance from the training staff before he can be activated.
"We want to sign off on it," Price told the Enquirer. "We want to be able to see what he's able to do. It doesn't necessarily have to be my eyes. We're going to want Dr. [Tim] Kremchek and the strength and conditioning people to sign off on his readiness.
"We've got to do that without having any concern that he's going to have any re-injury or setback. That's probably a more accurate assessment of where he's at."
Votto is batting .257 with six home runs and 12 RBIs this season.