White's leg issues

[Jenn]

I just quarantined my blue phase White's Tree Frog. He was having difficulty climbing out of his soaking bowl. When I reached in to pull him out and to figure out why, I realized he had no use of his back legs. They are not red at all but swollen at the thighs. It appears that clear white liquid is inside the bubbles. Looks like a pus filled blister only there is no redness at all. I've taken pictures to show.
Earlier today he was fine. Eating like crazy and jumping all over the tank. I left the house for 3 hours, come back and he has no use of his back legs. Still tries to chase crickets. Eyes are clear, skin is moist but he's dragging his back legs all over the tank. They simply aren't working. He's only about 1.5" inches long and there is nothing in the tank to "hurt" him.

Any ideas?