The news has gone from bad to worse for embattled Newcastle coach Michael Hagan after Test hooker Danny Buderus was told he would spend a further six weeks on the Knights' packed injury list.

Knights rake Buderus was expected to make a welcome return in last-placed Newcastle's next NRL match - a round four clash against North Queensland at Townsville - after sustaining a string of injuries on the Tri-Nations tour.

However, Hagan learned his injury-plagued Knights would need to hold on even longer without their inspirational No.9 who requires arthroscopic elbow and shoulder surgery.

Buderus, 26, will go under the knife next Tuesday, ensuring he misses Australia's ANZAC Test against New Zealand at Brisbane on April 22.

He has been tentatively pencilled in for Newcastle's round nine clash against Sydney Roosters.

Buderus was "extremely disappointed" that the injuries had not responded to treatment.

"I came back from England with foot, elbow and shoulder injuries," he said.

"The foot was operated on in January, I had a cortisone injection in my shoulder to settle down a cartilage problem and my elbow, which had some floating bone, settled down once I stopped training.

"Unfortunately, once I started picking up the intensity at training during the last couple of weeks, both the elbow and shoulder have flared up again.

"The only long-term solution is to clean them up with an arthroscope.

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