I am having a pain that seems to be centered in my left shoulder in the back under my shoulder blade. it feels like it s in the joint and sometime the weight of my arm alone, feels as thought my arm is going to come out of the socket. When I reach back, for instance, to put on a sweater, I get a sharp intense pain that lasts for a few seconds and then it goes away. When I move my arm in a circle, I feel a crunching sound and at time, my arm will ache down to my elbow . I believe I initially injured myself doing a push up in yoga .