The Bulls say Valentine underwent a previously scheduled left ankle stabilization procedure in Wisconsin. The team expects him to return to full basketball activities in about six months.
Valentine had yet to play this season.
He was initially diagnosed with a sprained left ankle during the team's September training camp and was expected to miss one to two weeks. But in late October, the Bulls announced he was suffering from a bone bruise, not a sprain, and would miss an additional two weeks.
Last season, Valentine averaged 10.2 points, 5.1 rebounds and 3.2 assists per game. He started 37 games, but he missed the final two weeks of the regular season after having surgery on his left knee.