Doug,
I tried to do the hip rotation exercise you described in your first post and I believe that when doing it, you may have extended your weight-bearing knee past your toes in doing it. This could very easily injure that knee. The knee should never extend past the toes, or it will put undue stress on the knee. I hope this might help out. Does this make sense?
janet dtantirojanarat
www.warriowoman.org