It could be a genetic deformity of weak or malformed bones. MBD or general calcium deficiency can happen in a hatchling if mom's nutrition levels weren't optimal for breeding. What's his current diet?
The vet should be able to tell, so you don't over dose on remedies if it's not MBD. It's too hard for me to say without knowing the species and common maladies. You'll want to get him a raised platform to get closer to the UVB, regardless.