Sometimes I feel a twitch in my leg,
Or maybe it's in my shoulder.
This type of thing seems to happen
More often as I get older.
I've talked with my doctor about it,
But she feels it's creating no harm.
"Muscles and nerves sometimes do this,
But it's really no cause for alarm."
Still, it can be quite annoying
Like someone is knocking on my skin.
I want to know if this knocker
Is trying to leave or get in.