Cattermole met a surgeon in London last week and was told he had damaged a tendon in his knee which was restricting his movement.
It is hoped an injection will aid the healing process and enable Cattermole to return to first-team action before the end of the month.
However, if the procedure fails, the only other option is an operation which would rule him out for the remainder of the season.
Martin O'Neill: “He went down to see the specialist and he gave him an injection.
“He's hoping that will cure things in the next couple of weeks, but if it doesn't we might have to have another look at things.
"He has missed a lot of the season and we have had to learn to cope without him.
“It's really Lee's career we are talking about rather than a two or three-week period here that might satisfy us.
“In the long term, it's more important to get it right.
“The specialist down in London, who has a very good reputation, thinks that the last thing you want to do is talk about surgery and things like that when it might not even be needed.
"I think that's the way you would have approached things anyway.
"But if that's not the case and it doesn't improve over the next couple of weeks, well fine.”