There is a pretty long discussion on it there.
And you are right - this is in the US. As far as patent goes = Copyright only protects the words that compose the pattern. If you wanted to protect your rights to a three dimensional object created from the pattern, you'd have to file for a *patent*. And you can't patent useful items, like clothing. And then as soon as anyone using the pattern changed *anything* about it, as in using a different colour, yarn, needle size, stitch, etc, it would nullify the patent. You would have to patent every possible incarnation of the pattern to cover yourself, providing what you were trying to patent wasn't deemed a useful article.
Not to mention patents being obscenely expensive.
I saw on Rav where a lady was giving out an Angry Birds pattern, and she had received a cease and desist letter. SHe had to rename the pattern to "Angry Fowl" and she was all good.