The move was made Tuesday, with Smeltzer scheduled to make his major league debut against the Milwaukee Brewers.
Smeltzer, 23, was acquired last season from the Los Angeles Dodgers in a trade for second baseman Brian Dozier. Smeltzer, a left-hander with a funky delivery, has a 1.15 ERA in nine starts this year between Double-A and Triple-A.
Pineda struck out six Brewers in six innings on Monday night. He allowed three runs and three hits without a walk. There was no sign of injury during or after the game.
Manager Rocco Baldelli said the decision was a preventative measure. Pineda suffered a small tear in the meniscus of that same knee last August that kept him out the last month of the season.
"This is more of a maintenance issue for us going forward and for Mike. Something that we knew we would have to talk about at some point," Baldelli said. "But taking an opportunity and giving him 10-ish days to get this taken care of. He'll continue on with his arm program and throwing. I don't foresee it being a long-term issue in any way. It's actually something that was kind of well thought out and something that we knew we'd be looking at."
Pineda, 4-3 with a 5.32 ERA in 11 starts this season, underwent Tommy John surgery in 2017.
Martin Perez, originally slated to start Tuesday, had his turn pushed back.
The Associated Press contributed to this report.