The same injury limited Thomas to just two games last season.
It isn't clear how much time he will miss. Thomas left the practice field on Wednesday after injuring himself and was expected to receive an MRI. He also had offseason surgery to repair a torn biceps.
Thomas, 28, is in his second season with the Colts and was projected to be the starter at left guard.
Thomas has also played for the New England Patriots, Detroit Lions and Miami Dolphins, the latter of which drafted him in the sixth round of the 2008 NFL draft. He signed a four-year, $14 million deal with Indianapolis in 2013.
- Scooby Axson