An MRI performed on Monday revealed no structural damage.
The Orioles debated on scratching Chris Tillman from Wednesday's start and going with lefty Zach Britton had Johnson not checked out, and sent two potential lineups to the Rays.
"Just out of professional courtesy to [Rays manager] Joe [Maddon] with Steve and everything today. I said there's an outside, outside chance," manager Buck Showalter said. "It's been Tilly all along."
Johnson said that he can go whenever the team needs him, and he is an option -- along with Joe Saunders -- to start Friday's Wild Card game against the Rangers.
"I have a [Jason] Hammel brace," Johnson joked. "I can feel it, but it's only going to help me out there, just to make sure I don't have too many lateral movements with my knee. It kind of keeps it in place. I didn't feel it one time out there. I feel good."
Pitching coach Rick Adair also rolled a ball off the mound to test Johnson's movement. Adair pronounced him good to go.