However, the Netherlands international is prepared to play through the pain and put any operation back until January to help Swansea through a hectic December schedule.
Michael Laudrup's side have six games in the next 20 days and Vorm is determined to assist the side's progression both domestically and in Europe.
"I have had some problems with my left knee for a while and I need to get it sorted," he said.
"It keeps swelling up. It has happened a couple of times in the last few weeks. We have tried to manage it and I have played a few games, but I have to leave it a while to be ready for the next game and it is getting worse and worse.
"I had a scan again on Monday and there is a tear in my knee which is a bit bigger. We knew then we had to do something about it.
"We will try to manage it this month, and then at the beginning of January I will have an operation and be out for around four weeks.
"We still have five or six games until the beginning of January. I hope my knee settles down and I can play but then we need to get it done, not only for Swansea but for the World Cup as well."
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