It is a devastating blow for the 27 year-old who underwent a full knee reconstruction on his other leg with his former club St Kilda at the beginning of the 2009 season.
Clarke joined the Lions during the 2009 AFL Trade Period in October after sitting out the entire 2009 season and commenced a strict rehabilitation program with his new Club.
He made his only senior appearance for the Lions against Melbourne in Round 18 last year at the Gabba before a hamstring tear suffered in the opening quarter prematurely ended his season.
The bitter disappointment of this latest set-back comes after Clarke had completed a near full pre-season training program.
