BLUE TONGUE SKINKS

I got my BTS last weekend and bought everything from the same person (exactly same enclosure, same positioning of hiding/water stuff...)

Today I noticed strange things with his leg. I recorded it here: https://vid.me/J5za

Is this normal behaviour?

Is this a case of "Metabolic Bone Disease"? I don't see any strange humps anywhere on his body. Is that just the first sign?

I have seen this in iguanas and bearded dragons as an early sign of MBD, but not sure about your bluey, how old is he?

About 8 years old.

I noticed that he's doing that only inside his enclosure. On the floor hes walking normal...

I've only seen it when reptiles are at rest, for example, a bearded dragon perched on his log and a toe twitching.

Oh, and it's usually an early sign, I wouldn't think MBD would be just appearing in an 8 year old. Maybe someone else has some input?