In both my right/left knee replacements, I had some type of a nerve block (don't remember the name). The right knee was a breeze and lasted 3 - 4 days which really helped with the initial pain after surgery. However, the left knee was totally different (actually the entire experience was & not a good one) and I came out of surgery feeling the pain immediately and it was awful! There was no scan of sorts to locate the nerve as my husband had prior to his shoulder repair. I think this really should be mandatory for accuracy. With both knees, I will occasionally get what I call "nerve zaps" which I have been told is normal. They are not really painful, but I definitely feel it. Wishing you the best with Mayo Clinic.