there is mononeuritis multiplex, which can cause a pretty random pattern of weakness.

But, there is also lupus myositis which can cause weakness in the thigh, and is painless. I don't know a lot about it, but I would rather suspect that it would effect both sides. It shows up in blood tests. I think there is also a primary version that can occur without lupus.

Have you had that mri yet? It would also be good to rule out small stroke seeing it affected your arm and leg on one side. Any facial weakness?

cheers
raglet