Almost forgot, don't freak out as it is more common for girls and between ages 1-4:
Nursemaid Elbow
She had this and we had 4 bouts of it happening. But even if it ever does happen, they will act like it is broken and won't move it. Whenever her arm joint pops that is the first thing in my mind now, but it hasn't happened since we were in Japan so we are over it. When it first happened I freaked out, but now I spread info about it so other parents while know.
