The Ulster star suffered the injury in training and will now undergo surgery to correct the damage.
Ferris is expected to be sidelined for six to eight weeks, ruling him out of the final Magners League game of the season and leaving him as a serious doubt for Ireland's summer schedule.
The 2009 Grand Slam winners face the All Blacks on June 12 before taking on the Maoris on June 18 and then traveling to Brisbane for a Test against Australia on June 26.
Ferris is no stranger to training ground injuries having torn the medial collateral ligament in his right knee during a training session with the 2009 Lions.
The 24-year-old had enjoyed a superb start to his first tour with Britain and Ireland's elite, scoring tries against the Golden Lions and the Cheetahs.
He had been tipped for a Test spot against the Springboks but was instead forced home before the international series had begun.