THE BRISBANE Lions are breathing a collective sigh of a relief after young defender Justin Clarke escaped serious injury following a heavy knock to the head at training on Monday.

Clarke copped a knee to the head in a marking content and fell to the ground heavily during the Lions' training session at Coorparoo.

The 22-year-old was taken to hospital in a neck brace, but scans revealed no break or fracture to Clarke's neck.

The club confirmed he was discharged from hospital on Tuesday and will be further assessed in the coming days before a decision will be made on when he returns to training.

Clarke has established himself as a key defender in the Lions' back six, having already clocked up 56 games in his three seasons at the club.