When we had our son I threw my back out for the first time in my life due to something called baby back bending over and lifting him in and out of the crib. Now, about once a year it will go out for a day or so when I lift something with my back and not my legs until it pops back into place like nothing happened - all pain gone in an instant.
That happened while walking the dog and kid to school this morning and I let out an audible FUCK YEAH frightening at least one other parent at school dropoff. Kid was out of earshot at least.