The Argentine midfielder fell awkwardly during Roma's 1-1 Serie A draw with Empoli on Saturday, appearing to catch his foot in the turf, under his body, as he turned.
The club confirmed the extent of the damage sustained in a statement on Sunday.
"Iturbe underwent tests this morning that revealed a distortive trauma to his right knee, with damage to the lateral collateral ligament," it read.
"Iturbe also suffered a strain to his right ankle and potential ligament damage.
"The player has already started treatment on the injury."
The 21-year-old is facing a lengthy spell on the sidelines, which will be a major blow to Roma after Dutch midfielder Strootman last week underwent further surgery on the knee ligament injury which forced him to miss last summer's FIFA World Cup.
But Iturbe remains positive, taking to social media on Sunday to share his thoughts.
"It is hard, but it's the reality. Now is the time to work hard and return stronger," he tweeted.
