Did you know that the only joint attaching your upper extremity to your body is one that, on average, is only about 1.5 cm wide? And nope, it’s not the shoulder joint…
It’s actually the joint between your sternum (breast bone) and your clavicle (collar bone) called the sterno-clavicular joint, that little bump that juts out from both sides of the big dimple at the base of your throat. Your shoulder joint connects the humerus (arm bone) to the scapula (shoulder blade), but technically the scapula is part of the extremity not the trunk. In fact, it isn’t attached to the rest of your body by anything other than muscles. So the old 
song Dem Bones wasn’t totally wrong in saying “the back bone connected to the shoulder bone” and “the shoulder bone connected to the neck bone.” But it wasn’t exactly right either…
Bottom line: The arm bone is connected to the shoulder bone, BUT… the shoulder bone isn’t (really) connected to the body!
