The Western Bulldogs have confirmed youngster Roarke Smith has a ruptured anterior cruciate ligament.

Smith went to ground while contesting a ball during the third quarter of his side's JLT Community Series loss to the Lions and was help off by a trainer.

It is a huge blow for the 20-year-old, who also underwent a knee reconstruction in August 2015.

The club confirmed on Friday afternoon he will undergo a traditional knee reconstruction.

“Scans today confirmed Roarke has ruptured his anterior cruciate ligament and he will undergo a traditional reconstruction on Monday," Bulldogs Head Physiotherapist and Medical Services Manager Chris Bell said.

“Roarke’s a highly regarded member of our playing group and we’ll put all our efforts into supporting him through his recovery.”

Smith, the No.5 pick in 2014 Rookie Draft, made his debut in round 22, 2015 and has played two senior games for the clubs.