Thanks for the ping! There’s some great posts on this thread. Some realism. Defending against a knife attack is a seriously iffy proposition. The attacker will likely have the initiative, and once he gets inside your reach you’ll be lucky to survive, training or no training. I agree with the posts about situational awareness being the key. Whatever few extra seconds of warning you can get may make the difference.
I like polearms. Even a stout staff (er... Walking stick) can extend your reach. Anything that lets you deliver blows, jabs, slashes or stabs at a greater range than the point of his knife is a step in the right direction.