Australian back row forward Wycliff Palu has undergone knee surgery to repair cartilage damage, continuing a race to regain fitness for this year's World Cup.

Palu is not expected to play for the Wallabies in the current Tri-Nations tournament, because of a cracked shoulder blade and the knee problem flared during a recent camp with the Australian squad.

A Wallabies spokesman said the surgery was minor and would not extend Palu's time on the sidelines.

He said the knee injury "was more an irritant than anything and there was an opportunity to [have the operation] now and get it done."

Palu is expected to make his playing return either in Sydney club rugby or for the Australian Barbarians against Canada on August 26.

However, a speedy recovery will be crucial for Palu's World Cup chances, with Australia coach Robbie Deans set to name his 30-man squad on August 19.

The forward's career has been plagued by injury, playing just six Super 15 matches for the Waratahs this year, while his 2010 season was aborted by a ligament tear which left him needing a knee reconstruction.

Fellow No.8 Richard Brown was ruled out of the New Zealand tournament Thursday, after booking in for shoulder surgery, leaving incumbent Ben McCalman, Scott Higginbotham and in-form veteran Radike Samo as the leading contenders.