Fulham boss Roy Hodgson has confirmed that Andy Johnson has had surgery on his groin in a bid to try and work out what the problem is.
Johnson missed Fulham's 1-1 draw with Bolton on Saturday and Hodgson confirmed that was because he has undergone an operation.
Johnson has been struggling with the injury since early October and despite intensive treatment, he has continued to suffer in pain.
"He had an operation on Saturday and I am waiting to hear what the results of that are," said Hodgson.
"It is pretty much exploratory because he has tried so hard to get back.
"There have been days when we thought he has cracked it and got manageable pain but then the following day when he comes out to training, he does not have manageable pain.
"He is forced to go back inside again and that was the case on Friday and the day before.
"That has prompted us, after the numerous scans and alternative medicine, to operate and go into the area where he is suffering the pain in the hope of finding out what it is and put it right. I fear he will be out for some time."