Just wanted to add that I have had a lot of pain after coming off of Xanax, and I know others coming off of benzos do, too. The most severe pain being in my legs, hips, and low back. I get the pain, twitching/spasming, and a burning feeling (especially in my legs).
You also mentioned you've had chronic back and leg pain. Out of curiosity, when did this begin? Before or during benzo usage? I only ask, because it wasn't until I was on the benzos that I started getting some pain in my back and down my right leg that was like a sciatic nerve pain. I never did see a doctor for it, but now I'm becoming convinced that pain started from being in tolerance on the Xanax (and possibly from my long-term Paxil use, too). I'm hoping as I heal, this problem will fully resolve. Actually, the type of pain and the location of the pain I was experiencing earlier on has already changed and intensities are lessening the longer I have been off the drugs, so I'm quite sure that was the problem all along. I guess time will tell!
I've also seen people mention that whatever types of aches and pains they dealt with prior to benzos, were temporarily magnified when coming off the benzo (due to how this affects the nerves and muscles, etc., and it seems like it sometimes targets those areas that were already vulnerable.).
Anyway, like [...] said, unless you did something recently to cause this, it sounds very typical when coming off these meds.