Bulls captain sidelined for four weeks
The 30-year-old prop has been troubled by a damaged cartilage in recent weeks.
Lynch, who played in yesterday's 52-6 Engage Super League thrashing by Huddersfield, will now miss matches against Crusaders, Warrington, Castleford and Hull.
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Hide AdBulls coach Steve McNamara said: "It's a measure of Andy's stature as a player and as captain that he has played through the pain barrier in recent weeks.
"He has never given less than 100% but the time has now come for him to have the operation with a view to being fully fit for the business end of the season."
The Bulls expect to learn today the extent of the knee injury suffered by back row James Donaldson in last week's Challenge Cup loss to Warrington.