I had the same experience, and you get an "A" in body awareness for noticing. It is pretty common, and totally correctable over time. My own theory is that it relates to the fact that the external rotators (the ones that turn your foot out) are some of the most traumatized muscles during the surgery. They are often cut or detached, before being repaired at the end of the surgery, so they are not very anxious to get back to work during the initial healing process.
The two things that I worked on were to be conscious of making my foot track straight ahead when I walked, and to work on strengthening the external rotators when the time came. When you are walking, try to be aware of the muscles that you need to activate to keep your foot tracking straight. The fact that you are aware of it, means you are already well on your way to getting past it.