According to my surgeon he found chipped away bone from the
clavicle, which is why the bump formed it. It is just ossification
of the
clavicle, which usually ossifies before other bones. You probably damaged your clavicle sometime in your life, but never new until you got older and the osteoarthritis started setting it. Basically, you think the bump formed a year ago, when in fact, it has been around longer than your think. Just notice because it is starting to hurt you, which is normal.