Given the data you have given us it doesant seems to me that is MBD

However give im some more veggys there are lots of things that you can try. Water cress, dandilions, hybiscus, clover, figs ,alfafa ,spineless opuncia, rabits hay,etc. And change your uv bulb by a new 10.0 like powersun(Im not a big fan of this "fry you lizard brains lamps", but this is just what this guys like and need

). Im thinking 2 things that could cause this: artritis ,bonne cancer or a infection. Touch your lizards swollen leg. If the lump is really hard(bonne hard) and ataches to the bonne or makes part of it it is either artritis(much more likely) or some kind of tumor. Or if the lump fells soft or even like there is some kind of harder material inside of it, there is very high possibility that is a infection and the lump is a big pus ball

Try to strech very delicatly your lizard leg. That will help you to analize it. Lets start by that and then we will see.

I would say there is a 95% of chance that is either artritis or a infection and both are treatable
