and if you can't do the pivot, say there is a bunch of folks or a wall or a row of table/chair blocking, then what?
Good question... Surely the collective wisdom of Aikiweb has possible answers? Hypothetically, strike to the eyes with the hand on the grabbed shoulder, very hard kick to the shin/knee, some form of block to the arm that has the knife? I'm speculating. take the initiative and offer a "glasgow kiss" of your own? Can't lose awareness of the knife.. I count myself fortunate in that I've never bumped into this "out there"...
And of course, anyone can offer "what if" ad nauseum.. What if nobody ever attacks you "out there" Have we wasted all those years of training? Have we developed skills and fitness through doing something we enjoy that also provides potentially useful abilities?