Gawn underwent scans this morning, which confirmed a medial meniscus tear of the right knee.
The full extent of the injury, including how much football Gawn will miss, will be determined after he has been operated on and further investigation has been completed by the surgeon in the operating theatre.
Gawn, who turns 20 years old on December 30, played four matches in 2011 after making his AFL debut in round 11 against Essendon.
He was selected at No.34 in the 2009 NAB AFL Draft.
The club will provide a further update once all details are clear.