Oh maaaaan! Anyone heard of Nursemaid's Elbow? I hadn't until today. I picked up my younger daughter by the hands and her little elbow came out of joint. It wasn't rough or anything, I was just picking her up in a silly way while we were playing. She wasn't in any pain, but her arm was just hanging down by her side, limp. I guess it's very common and super easy to happen up to age 4. Just a warning! Also, it took the doctor literally (not figuratively) 3 seconds to put it back in place.
Moral ...