Oscar McDonald is helped off the field during Fremantle's clash against Brisbane in round one, 2024. Picture: AFL Photos

FREMANTLE defender Oscar McDonald could miss the rest of the season after scans showed he requires knee surgery.

McDonald injured his left knee during an awkward landing in Fremantle's season-opening win over Brisbane.

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The swelling around his knee was so bad that medical experts were initially unable to give a full diagnosis on the injury.

Further scans have shown damage to his posterior lateral corner (PLC) and some damage to his anterior cruciate ligament (ACL).

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PLC injuries are considered traumatic, and are notoriously difficult to diagnose because of the complex anatomy of the area.

McDonald has been booked in to undergo surgery to fix his PLC on Wednesday.

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During that procedure, the surgeon will also review McDonald's ACL to determine whether that needs to be surgically repaired as well.

Fremantle says it will put a return-to-play timeline on McDonald after he's had surgery. The injury is a cruel blow to McDonald, who received a lifeline from the Dockers at the end of last year following previous stints with Melbourne and Carlton.

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McDonald signed a two-year deal with the Dockers as a delisted free agent.

With fellow defender Brennan Cox set to miss a further 10-12 weeks with a hamstring tear, 20-year-old Josh Draper has filled the void over the past two games.

Fremantle will be aiming to make it four straight wins when it takes on Carlton at Adelaide Oval on Saturday.