I've been wondering the same thing! What are the norms here? It seems like the basic top-down sock, for instance, is such a standard. How can you avoid duplicating what others have done? And are you supposed to try, with such a basic pattern?! If you want to just make a basic sock, how do you go about claiming such a pattern as your own? It seems like people do it all the time, publishing "your basic sock pattern," and they are all very very similar!
Certainly, you can always make it your own by adding some kind of color or texture pattern to it....
I was talking to a lawyer who specializes in copyright of creative material (mostly music and art), and he said that if you are the one determining the gauge, the color, the size, and any shaping options, then all these factors serve to make it your own.
I'd love to hear anything you find out about the topic!