St Kilda announced on its club website that Markworth, 20, would undergo surgery this week to repair the anterior cruciate ligament he injured during a skills session at the Saints' training camp in Colorado earlier this month.
The Saints said a timeline for Markworth’s recovery would be determined following surgery, but given the recovery period for a knee reconstruction can be up to 12 months he is unlikely to play until late next season at the earliest.
Markworth is yet to play a game for the Saints after being drafted by with pick No. 35 in 2011's NAB AFL Draft.
However, he could reasonably have targeted next year to make his AFL debut after being named as an emergency for the Saints in several games in the second half of 2012.
Meanwhile, St Kilda president Greg Westaway announced at the Saints' annual general meeting on Wednesday night that he would step down at the end of 2013.
Westaway, 70, has held the Saints presidency since taking over from Rod Butterss late in 2007.
The founder of Gregorys Transport, Westaway has been a St Kilda member and sponsor for more than 20 years.
His pending departure comes as the Saints announced an operating profit of $631,135 in 2012, a $2.1 million turnaround on 2011.
In his time as president, Westaway has overseen a change of the Saints' board and the appointment of senior coach Scott Watters at the end of 2011.
Nick Bowen is a reporter with AFL.com.au. Follow him on Twitter: @AFL_Nick
