It’s realistic in the sense that it can and does happen. At the same time, it
probably won’t save your life. Knife wounds to the palms, (called, “defensive
wounds,”) are fairly common when someone has been attacked by a knife wielding
opponent. Usually, what happens is they’ll attempt to block the knife by
putting up their hands, palms out, and their palms and fingers will take the
initial assault. That I’m most familiar with the term from autopsies should say
a lot about how well this usually works out for the victim.
dealing with a situation, where someone’s trying to stab you and your only
option is to catch the blade with your hand, it is better than dying. However,
it is also a very temporary solution, and one you can’t repeat after using. It’s
also, probably, not your best option.
bleed, your body is trying to do two things; first clean the wound and expel
any foreign objects in it, then seal the wound over to allow the tissue to heal.
Fresh blood is aggravatingly slick. Once exposed to oxygen, blood becomes tacky
and coagulates over the course of a few minutes. (Specific clotting times vary
based on a number of factors. For example: if your character is an alcoholic,
their blood’s ability to clot will be severely impaired.) It only remains tacky
for a few minutes, and will then harden into a solid mass, so the window here
is fairly narrow.
take a knife to the hand, you’re going to bleed all over your hand. That means
your hands will get slick, and have a harder time gripping the blade. This is
before you consider the part where your hand is actually getting cut to pieces.
Eventually the blood will clot (whether you survive long enough to see this or
not), at which point gripping the blade would become easier, but that’s not a
realistic consideration because the fight won’t last long enough to get there.
said before, your body functions on a kind of pulley system. Your muscles pull
on tendons which in turn tense against your skeleton, causing your limbs to
move. When you start cutting tendons, the pulley system starts to break down.
Some of the most delicate pieces of this system are in your hands and feet.
Start carving those apart, and your hand will
not work. This isn’t an, “oh, I can force my way through on sheer
willpower,” situation. The mechanical components critical to making your hands
work will be damaged or destroyed. The spirit may be willing, but the flesh has
been turned into butterflyed steak. Catching a knife with your hand will stop
that strike, but it means your hand will
not work again. Yes, if you survive, it can be repaired surgically, but
that’s not going to keep you alive.
better option, if you have sufficient manual dexterity to catch the blade is to
catch your opponent’s wrist instead. Again, this isn’t a great position to be
in, and wrist grabs are some of the weakest and riskiest holds, but it is far better than trying to grab their
knife. Your arm or hand might get nicked by the blade, but that is vastly
preferable to taking a direct blade to the hand. Going for the wrist is a
legitimate strategy and a part of some knife fighting doctrine. Granted, your
best option would be to maintain distance, and never let a knife wielder get
close enough to attack, but that’s not always a practical option.