An MRI on Saturday showed a strain but no torn ligaments. Rangers manager Ron Washington says there was no timetable for Treanor's return, but surgery is not necessary.
Treanor, who arrived at Rangers Ballpark before Saturday's game against the Angels wearing a big brace and using crutches, said he'll know more about a possible timeframe for his return in about 7-10 days.
"I get upset because I want to be with team," Treanor said. "I've started the therapy to get the swelling out. I'm thinking 15 days, the DL time, is what I'm aiming for to be ready to play."
Treanor hurt the knee in the seventh inning of Friday's game with the Los Angeles Angels. He was running to first and clipped the foot of first baseman Kevin Frandsen, falling to the ground. He was on crutches in the clubhouse after the game.
Treanor is hitting .225 with five homers and 23 RBIs in 64 games this season. The most games he's played in a season was 67 in 2006 with Florida.
Teagarden, who started the season on the Rangers' roster, was hitting .242 with three homers and 32 RBIs for Frisco.
The Rangers chose Teagarden over Max Ramirez and Jarrod Saltalamacchia, who also have major league experience, because they feel Teagarden is the best defensive catcher in that group. Teagarden said he used his time at Frisco to work on the mechanics of his swing and to improve his throwing and blocking behind home plate.
"I used it almost as a practice environment," Teagarden said. "I was working on a lot of different things, changing things, seeing what was working for me. I had some ups and downs down there, but it was a good environment for me to play in."
Teagarden admitted that he wondered where exactly he was on the depth chart after going from the majors to Double-A early in the season.
"With the team doing as well as they have up here, it wasn't easy for me to think I'd be coming up here any time soon," Teagarden said. "But with an injury like that, anything can happen. I'm grateful to be here and help contribute. Anything I can do, I'll be ready."