B52s the elbow thing happened to us - DS1 sat down in the middle of the road as a protest whilst crossing and I pulled him up by one arm to get him out the way of a car.
We went to A and E, were ushered straight in, and about 5 consultants suddenly crowded into the cubicle with big grins on their faces. "Oh good" the chief one said, "We have been hoping one of these would come in. We've just got a research grant to look into it. This happens to a lot of toddlers. We've ordered some new equipment to scan their elbows, and it's coming next week." He then picked up DS1's arm, did a nifty little manoeuvre and lo and behold it popped back in. DS1 was cured. Best A and E experience we have ever had.
We found later on that DS1 is somewhat hypermobile in his joints, and that sometimes his knee pops out a bit too. We have worked out how to pop it back by wiggling it around a bit and pushing, and he can now do it for himself, so we don't need to go to the doctor with it.