I see some major husbandry issues tht may be causing the problems. UVB lights give light, but they only give UVB rays for 6 months. The Dragon needs UVB and a calcium supplement to prevent Metabolic Bone Disease which I believe you are seeing. It can cause multiple issues in the health of the Dragon. This is information on MBD:
There are quite a few changes needed. Over the age of one a Dragon needs 80% Veggies like collard greens, mustard greens, Butternut squash, Escarole, Curly endives and dandelion greens. They only should get 20% live prey, since too much insect protein can cause gout, and kidney failure, which are alos possibilities with the swelling in the legs.
The Dragon needs to see a Herp Vet for a positive diagnosis, but you will need to make some changes to help the Dragon.
Remove the sand, and replace with tile, cage carpet or paper. Get a new UVB bulb that is a linear tube Reptisun 10.0 and put it no more than 12 " from the Dragon. Add a good plain calcium to the Diet a. Start the Veggies asap. I can locate a Herp Vet for you with a State. The changes will need to be done to help the Dragon to recover. MBD is very painful and not only affects the skeletal system, but the organs too. Please let me know if you need a Vet