Leonardo Bonucci revealed he "heard a crack" before being carried off on a stretcher in Italy's 4-1 friendly defeat to Germany.
Bonucci's knee appeared to buckle as he attempted to stop a Mario Gotze flick in the lead-up to Germany's third goal, finished off by Jonas Hector just before the hour mark.
Mesut Ozil completed the rout in Munich with 15 minutes to go via a spot-kick, adding to Gotze and Toni Kroos' first-half efforts, condemning Italy to their first loss against Germany since 1995.
Bonucci said he is unsure of what type of injury he sustained, but the 28-year-old will undergo tests to examine the full extent of the damage.
"I heard a crack and I was in a bit of pain," the Juventus defender told Rai Sport.
"I do not know exactly where I got hurt. It could be anything.
"We'll see what the tests say tomorrow [Wednesday] and what happens next."