Both of mine went inward a little and stayed that way, well, inward compared to pre-surgery. I'm no where near pidgeon-toed, if anything I still walk like a duck, but less so than I used to. I could see some swelling and soft tissue changes causing some oddness in the first few weeks after surgery, but I do think there is a bone component to the toeing inward deal.
I think it's related to the acetabular cleanup during surgery. One of the simple tests the doc did when I first visited was to quickly push on my knee inward, while I was sitting, to see how stiff and how not far it goes in with a light push. Another test was done with me on my back, the doc put my feet together and moved the legs into a crouching position (knees toward chest). The knees quickly went outward and the feet crossed at the maximum crouched position, which wasn't very far up. I believe bone buildup on the inside edge of the acetabulum is an obvious sign and maybe even one of the first signs of OA. As the femur "deepens" into the socket, the tendency is for the leg to go more outward and duck like.
Anyway, I can now easilly move my knees inward, I can not think too hard about keeping my feet relatively straight while running, and I can even crouch and do a Conan O'Brien jump move with knees together heading for my teeth. Sweet huh?