My heel even hurts to drive because it rests on the floor of the car. If I'm driving an hour or longer I wear my Vionic flip flops, even in the dead of winter, but I do have appropriate shoes with me.
At first my knees felt funny, but they do warn you to break them in slowly because of the rest of your body and how they realign things. After wearing them intermittently for a few days everything was fine. They even help my back pain so I make sure I've got them on when cooking or cleaning.