yes, please post a pic. is there any underbite? any deformity at all to the hips or spine? swollen limbs?

it sounds like it's likely either MBD or an old break (or both). 

MBD can be halted, but not really reversed much. proper supplementation without overdoing it and proper UVB are the keys. it sounds like you have him in pretty good hands. what's the UVB in your tube? also, I"m guessing you already know this, but UVB burns out readily and the bulbs should be swapped out yearly or even faster. a lot of exotic vets will let you bring in a bulb and test it with their meters (at least our vets here do that).

supplement not substrate... Thanks Aimee, I'll post some pictures when I get home tonight. To me, it does not look like he has any deformity in his hips and his limbs look pretty normal. He does not do it very often so I'll try to catch him doing it when he eats tonight.

I'll look for an underbite as well.

Also, he is under a ZooMed Reptisun 5.0 UVB tube. Brand new as of yesterday.

5.0 is pretty skimpy for a beardie. they need some really intense UV for healthy bones. I'd go at least a 10, but the best is a good mercury vapor. what's your hottest basking temp for him?

Alright I'll go grab one on my way home! His basking temp was at 103 when I checked this morning. 

I added soe pictures to his gallery with a view of his back a right wrist

I'm guessing MBD, tho I've seen more severe cases, sadly. it might be a good idea to get him to a vet for a splint; if it's not a break, it might become one.