Wallaby prop Benn Robinson has been ruled out of the game for the rest of the international season.

The 26-year-old, who celebrates his 27th birthday next Tuesday,  underwent an arthroscopy in Sydney on Wednesday after stumbling at training on Tuesday and feeling a "click" in his knee.

While the injury at first didn't appear serious, further examination Wednesday has shown that he has torn the anterior cruciate ligament of his right knee, while also damaging a meniscus in the joint.

An operation in the coming days will be required to repair the damage, with the timeline required for recovery curtailing the rest of his season.

"It's disappointing news for Benn, disappointing news for the rest of the squad and for Australian Rugby as a whole," Wallabies coach Robbie Deans said.

"No one likes to see injuries like this. The seemingly innocuous circumstances in which it occurred only adds to the frustration, but injuries have always been a part of the game.

"When the door closes for one player, it opens for another and I'm sure the other front rowers we have will step up to fill the void Benn leaves.

"As far as Benn goes, we wish him all the best for his recovery and will be providing him with any assistance he needs."

Robinson had been scheduled to feature in his 43rd Test during Sunday's encounter with Samoa in Sydney.

Western Force prop Pekahou Cowan and Waratahs prop Al Baxter have both joined the Wallabies in training on Wednesday, with Baxter featuring in both of the day's sessions - while Cowan arrived in from Perth in time to join the afternoon session.

Both players were involved in the recent national scrum camps that were held by the Australian Rugby Union.

A decision on which of those players replaces Robinson in the Wallabies squad, and in Sunday's match day playing roster, will be made prior to the weekend.

As well as covering for Robinson, the pair's presence will also assist in team preparations while fellow props Ben Daley (shoulder), James Slipper (ankle) and Salesi Ma'afu (rehabilitating after an arm fracture) are unavailable for selection.