Was confused about what you were asking as you didn't mention you have been diagnosed with MS in your first post.
I would let your Neuro address the problem with your knee buckling. Have you talk to him/her about this. You should if you haven't.
I would recommend posting in the MS forum as well.
My neuro ran test and I was dx with Ms July 2010. I am on rebif and doing well except for knee buckling. I was really ill at first after neuro put me on this med rebif, I am better now.
Physician's visit?
Other symptoms?
This does NOT mean this is MS.