is it almost like this   

thats it exactly

wish I could help. that wa sa pic of my rescue.. looks like a past MBD issue and potential gout. Eats like a monster though and walks fine

hmm, shes not doin so well. i think she may not be getting the right calcium. though she had plenty in the cage they gave us ...

weird..it triple posted the photo.    Put calcium on her food.  It's better that way!

yea, the repi-boost stuff has that. and lots of protien. she'll lick it up pretty good thankfully. but not much, which i can understand

Articular gout is the most likely culprit, and unfortunately it's quite common in captive reptiles including leopard geckos. 

The pathophysiology of gout in reptiles is poorly understood - almost all our info is extrapolated from the human literature! - but the consistent risk factors seem to be renal issues (often from the use of certain antibiotics), dehydration, and inappropriate levels (or lack) of protein in the diet. Basically what happens is you get a perfect storm of physiologic and environmental factors that come together to increase the amount of normal uric acid in the blood ("hyperuricemia").  And when the concentration of a solute in solution gets high enough, what happens?  A precipitate - in this case urate crystals - comes out of solution to make an insoluble solid.  Since crystals don't flow easily through blood vessels, they tend to get stuck in tight places.  And since the joints represent the very tightest spaces blood flows through, this is where they accumulate.  These accumulations are responsible for the hard nodules you see at the joints. 

If you're imagining that this is probably very painful, you're probably right.  Although reptiles, being very stoic creatures, are very good at compensating for their condition, it's safe to assume their quality of life is compromised, especially as the syndrome progresses.  Prognosis at advanced stages is typicallly considered "poor," but you have a few options.

Identifying and correcting the husbandry can stop the progression of disease, significantly improve the animal's quality of life, and may even help reduce symptoms over a long enough period of time.  This should be done regardless.  Corrective treatment is difficult though, especially since it's hard to find vets equipped to address gout.  Allopurinol (or other antihyperuricemics) and antiinflammatory drugs may help to reverse signs of disease, but I can't verify whether that's even been attempted in a leopard gecko.

Get any lizard that looks like the one in the picture to a good, qualified reptile veterinarian.  Discuss treatment options and prognoses with your doctor, and consider euthanasia if there's nothing you can do to correct his condition or improve his quality of life.  Good luck!

thanks, i dont know if we can afford a vet. But we'll see how she does with eating blended food for a few days, we had a water dragon get better from gout pretty ok. but his wasnt as sevier as hers is