The 6-foot-4 Hornsby suffered the injury in the first half of a loss to Tennessee on Saturday and played only 12 minutes.
LSU coach Johnny Jones said he hasn't received the final report from X-rays and testing Hornsby underwent Sunday night but expected to learn more later Monday.
"He's had his X-rays, and we're not sure exactly the extent of Hornsby's injury right now," Jones said Monday. "We do know he will be slowed down for a bit."
Jones acknowledged that Hornsby could miss the remainder of the season.
Hornsby, the son of musician Bruce Hornsby, missed the first seven games of the season with a hernia injury and has been playing for most of 2015-16 at less than 100 percent, multiple sources told ESPN.
However, Hornsby was averaging 13.1 points in 20 games and shooting 41.5 percent from beyond the arc. He had averaged 18 points and made 14 of 31 shots from deep in the four games prior to the loss to the Vols.
LSU is 16-11 (9-5 SEC) and listed in the next four out of Joe Lunardi's Monday morning bracket projection. The Tigers play at Arkansas on Tuesday night and have four regular-season games remaining before the SEC tournament.