Lord Sessadore said:Think about this for a minute - if you were fighting someone equipped with any kind of sharp, pointy thing who was approximately your equal in fighting skill, would you honestly try to rush him and grab him? Personally, I would also use my sharp pointy thing to sharply stick the point in him before he does so to me.
You mean like most combats against plate mail wearing opponents played out when you lacked a heavy weapon?
Grappling (with daggers) was a common tactic against heavily armoured enemies and all knights were trained in it.