BRL-
You were pretty close to have not done it.
If you are just field-dressing (gutting) the animal in the field then any good sharp knife will work. I have used 2''-3'' folders quite a few times. If you are going to be processing the whole animal down into freezer packages, or quartering it up to be packed out..then a larger, heavier knife is needed. I personally use a saw to cut the large bones.
My father still uses what his father taught him to use for hunting: an old butcher knife and a common razor blade.