Why does Sidious use a cane?
We know that Yoda's cane could provide him with nutrients and anesthetics; not to mention that jedi morals forbid the abuse of powers to sustain yourself indefinitely.
My Star Wars Visual Dictionary states that the Emperor used the cane because he wanted to appear weak, not because he needed it.
Why do you think this is? To test for mutiny among potentially over-confident military officers?