PORT Adelaide midfielder Tom Rockliff has suffered a rare setback, with scans this week revealing the veteran ball-winner injured both of his knees in the same incident in the SANFL last weekend.

Rockliff's left knee injury was confirmed by the Power on Tuesday after he went down after a marking contest in the Port Magpies game. Scans had shown that he had a medial ligament sprain and would miss at least six weeks with his leg still in a brace.

But the former Brisbane skipper's bad luck didn't stop there, with Rockliff's right knee becoming painful and swollen in the days following the game.

MEDICAL ROOM The full AFL injury list

Further scans showed that he had also injured that knee, with the 31-year-old undergoing meniscus surgery on Thursday to rectify the issue.

The club believes the injury is likely to have occurred in the same incident as the left knee injury.

The secondary knee injury, however, is not expected to extend Rockliff's estimated time on the sidelines, with the club saying his timeframe out of action would likely remain the same.

Rockliff played the Kangaroos in round one but was made the Power's unused medical substitute in round two against Essendon and had been looking to break back into the club's midfield unit.