It's easy to question and doubt when you've never had the problem, but it's hell when it's happening to you.
A couple of years ago my back pretty much up and quit on me. It would take me 10 minutes to make my way out of bed in the morning, another hour to straighten out, and then I would not dare sit down all day because if I did I'd need to go through the whole process at once.
Saw a specialist who sent me for every test imaginable. X-Ray, CAT scan, MRI, you name it. Didn't find anything.
I ran my own business at the time, so I certainly wasn't looking for time off, and I didn't take any.
I don't touch painkillers or anti-inflammatories. Doctor tried to push them on me, but I refused.
Through my own research I figured that I was having SI joint pain or Piriformis Syndrome or both.
I started doing a few stretches that I saw online. More importantly, I stopped moving around in the careful way that a person moves when they have back pain and fear throwing their back out completely. This is what causes spasms, and if you don't have a back that is about to give out but have Piriformis, which is essentially a spasm problem to begin with, then walking around like that compounds the issue and prolongs and multiplies it.
This worked for me, but I acknowledge that I self-diagnosed and may not know what in hell I'm talking about. It's also very possible that it was another undiagnosed condition that simply cleared up on its own around the time I started trying to self remedy.
In any case, it was no joke. Just because the doctors can't figure it out doesn't mean it doesn't exist.