Ferris, 27, who has played only four times for Ulster this season and last started for Ireland in last year's Six Nations, underwent surgery on Wednesday and will take no part in the rest of Ulster's Heineken Cup campaign.
He was part of the Lions squad who travelled to South Africa four years ago but injury ended his tour before the three test matches against the Springboks.
"Although he had made excellent progress, some minor issues still remained," Ulster said in a statement. "Stephen will be out of rugby for a further three months but following this period is expected to make a full return to the game."
Ireland lock Paul O'Connell, who captained the Lions in South Africa but who has managed only two games for his provincial side Munster this season, has said that his return from injury in April may come too late to earn a place in Warren Gatland's squad.
O'Connell and Ferris are among a number of injured players who have missed Ireland's disappointing Six Nations campaign this season.
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