An injury caused a large joint effusion w/ elevation of the anterior & posterior fat pads on elbow. will the fat pads heal and return to its place?

Kind of: The fat pads are normal structures and so they don't really heal. In a x-ray of a normal elbow, they are usually not seen as they are within the joint. When the elbow joint has extra fluid in it, they float out of the joint and are visible. So when you see fat pads on an x-ray, that is a sign of a significant elbow injury even if a fracture is not seen, as in an occult radial head fracture.