I broke my shoulder blade a few years ago. Now I'm starting to feel and hear it thump when I raise my arm. Is my old injury related to this thumping?

Chances are good that the two problems are related. The thumping noise is a pretty good indication that the problem relates to the bones rather than the soft tissues. A condition called snapping scapula syndrome can start from problems in the bones of the scapula or rib cage, or from the soft tissues between. Sometimes snapping scapula can after a scapula fracture. This may occur because the bones on each side of the fracture don't line up smoothly, or it could be from irritation, swelling, or wasting (atrophy) of the muscles under the scapula.