Herschel can be seen walking without crutches towards the end of S04E01. Does he have a wooden leg?
He has a prosthetic leg now. When he kneels down to talk to Rick in their new farm, you can see it.
There is also a scene in that same episode where we see Herchels prosthetic on the floor and then the camera pans up so we see Herschel scratching his stump! it is around 40.07