When I first injured my right shoulder in 2010 I joined the ranks of circus performers, acrobats, dancers, and athletes with shoulder injuries. I was bummed out, but far from alone. It is one of the most common sites for pain and injury for anyone who engages in vigorous upper body activities from aerial arts to lifting groceries out of the trunk. And it’s no wonder. Shoulders are a complicated piece of equipment and, even though most of us have them, they didn’t come with an instruction manual. When I started