Rule changes have reduced the incidence of "ruckman's knee", though that is little consolation for East Fremantle's Rob Young as he faces three months out of action.

Young will be in a knee brace for the next six weeks after rupturing a posterior cruciate ligament and will require a long rehabilitation before he can play again.

Young, who turned 28 yesterday, damaged the joint when he and Swan Districts ruckman Wes Lammie clashed knees early at East Fremantle Oval last Saturday.

"It was just my turn," Young said, after his surgeon confirmed the initial fears over the extent of the injury. "Fifty per cent of ruckmen cop this injury and now I have to suck it up and get on with things."

Young also suffered medial ligament damage and bone bruising when the two 103kg ruckmen made knee-on-knee contact.

PCL injuries have reduced since 2005 when a 10m centre circle was introduced to restrict the run-up of opposing ruckmen.

East Fremantle's ability to go one better than last year's grand final defeat will be sorely tested with Young out of action until June.

The Sharks consider Young to be their most important player because of his ability to have an impact in the ruck and in key positions at both ends of the ground.

Young was ranked No.16 in _The West Australian's _ top 40 WAFL players this year.