First I drive a big rig. I have been diagnosed with my bones dissolving. Thursday 12/24/15 I went to get up from the drivers seat and I had to sit right back down. It felt like someone took a large needle and stabbed me with it on the inside on my left butt cheek . I did not have my billfold in my left pocket, it was on the dash. After a few seconds it went away till I put my left foot down to step on the left step to get out of the truck. Since the every time I go to get up, lean forward or shift in any kind of seat I get the same pain. Sometimes I even get it just sitting. It is so sharp it almost takes my breath away Does anyone know what might be causing this ?.