PORT Adelaide young tall Dougal Howard has had surgery to repair the ruptured anterior cruciate ligament in his left knee.

The 20-year-old sustained the season-ending injury after colliding into Fremantle speedster Michael Walters in the third term of Saturday's 17-point loss and limped off the ground. 

Power high performance manager Darren Burgess said Howard would be sidelined for around the next 12 months.

"In terms of the surgery, it all went well for 'Dougs', unfortunately it's a pretty long road recovering from ACL injuries," Burgess told portadelaidefc.com.au on Monday night.

"It's too early to say how long the rehab will actually take, but often it's a return around the 12-month mark.

"He'll be spending the next month trying to keep the knee stable and rested, and from there he'll progress into a strength and mobility program."

The injury puts more pressure on the Power's already decimated ruck stocks.

Howard shouldered much of Port's ruck duties since first-choice ruckman Matthew Lobbe ruptured his PCL in the SANFL at the start of May, while fellow tall Paddy Ryder is serving his year-long doping ban.