you can try practiceing with one arm tied behind your back, or in a squating position, sitting position, duck walk position. you can try no arms

. try from the point when the knife touches your body. Have the person attack you from behind. Add more then one attacker. Add a kick or punch before the knife is used.
you could also get a couple friends to tie ropes to your arms and legs, and at random pull the ropes rendering the arm/leg useless in the middle of the knife exersice.
try it blindfolded even!
theres no real need for this post, just some ideas for training...
thanks for your time.