All my back and other joint issues are in my info block below my post.
I have this "thing" that happens to me and the Drs & PT can not give it a name and remain clueless how to help. They say what I am describing is not something they can pin point.
So I will attempt to do it here.
This is only on my right side - which according to all my tests is my good side disks, nerve etc wise. Which is also why everyone is clueless.
This can happen to me with 2 totally different extremes.
It can be after I did too much in a day - such as say I did laundry and went shopping, for me that is too much.
Or it can happen from me reaching up to scratch my nose - and no I am not exaggerating or kidding.
Here is what "it" is.
The right lower area about the top of my hip leave but in my back "crumbles" - gives way - feels like nothing is there - feels VERY VERY weak - feels empty - feels like an accordion that was opened and now is closed - a rubber band that was tight and now is snapped ( these are all the things I have used to describe this feeling to my Drs & PT ). I can not walk with help from a person. My cane does not work for me when this happens. I need a person to hold me up.
The pain is just over the top when this is happening. Pain unlike any I have ever felt. It is not steady it comes with all the feelings I described above. These feelings happen with the slightest movement.
The pain is a stabbing pain - the type the makes you jerk forward, like you were just stab in the lower back.
The pain is so bad I can not help but to scream out when it hits me. I normally can grit through the worst of pains with maybe a groan. With this pain I scream involuntarily.
When this happens my husband has to undress me, put me to bed, get me on and off the pot etc.
I get no pain relief from nothing I do or take. Except I go to bed and stay there for at least 8 hrs and get back up feeling a tad more sore then I normally do but other wise it is like nothing happened the night before.
This has never happened to me in the mornings or even mid day - it is always in the evenings.
I hope someone here can make sense of this, so I know another way to present this to my Drs and/or PT people.
Thanks in advance to all who read 
Ms. Humpty Dumpty Took a great fall and all the Drs and surgeons could not put her back together again.
After my fall I started to fall apart. L1-L2-L3-L4 - S1 & S2 gone. ( full herniation )Spinal stenosis, spinal arthritis, degenerative disk, scoliosis.
The spacers in your back are gone/going, spinal nerve damage.
Spinal spurs. Both knee caps & both hips have degenerative bone disease, arthritis and bone spurs.
No surgeries as Drs. don't think it will help and may make things worse.
Age 47 - Here to find & offer support.
I have no idea what this might be. I have not experienced anything of the sort. What I am wondering ... thinking out loud here, is do you have issues with your facets? Is it possible that you are "locking up" like many others have described and when in that locked position you get that weird feeling because the muscles are out of play?
I hope that your docs can find an answer for you soon.
"C"
"Reality is the mirror of your thoughts. Choose well what you put in front of the mirror"
- Unknown
but whatever it is sounds like maybe a result of your right side compensating for the left side? Sometimes the compensating our bodies do cause even more problems.
Microdiscectomy L4-L5 Dec '07
<(unrelated) Resection of left liver lobe for 6.5cm benign tumor June '09>
MRI Oct '09,ESI Oct '09, ESI #2 Nov '09
Jan 26 Laminectomy/subtotal discectomy L4-L5
Ms. Humpty Dumpty Took a great fall and all the Drs and surgeons could not put her back together again.
After my fall I started to fall apart. L1-L2-L3-L4 - S1 & S2 gone. ( full herniation )Spinal stenosis, spinal arthritis, degenerative disk, scoliosis.
The spacers in your back are gone/going, spinal nerve damage.
Spinal spurs. Both knee caps & both hips have degenerative bone disease, arthritis and bone spurs.
No surgeries as Drs. don't think it will help and may make things worse.
Age 47 - Here to find & offer support.
If something happens so suddenly and so severely, I wonder if there is a disc or bone fragment that is floating around and getting pinched with movement..it could be anywhere, within the spinal canal or in the foramen. If rest for 8 hours lessons the pain and leaves you sore but functioning, then this fragment could have settled back into place.
It would take very special CT scan or MRI found only at major centers to isolate this.
Just my thought.