Can a judgement entered without your knowledge and then put on your credit report without your knowledge be removed?

Yes and no,

You will have to go to court and get the actual judgement overturned.

You will have to see how they did the legal service ( were you notified of the court case) if they did a legal service then it is a valid judgement.

If they knew where you were at, and did not properly serve you, then you can file to have this judgement set aside. Of course they can always just file a new one against you.