A study of the history of the 2A quickly reveals that the arms of which it speaks are the weapons typically used by an individual for civilian purposes (such as, but not limited to, hunting and personal protection), but that, in a pinch, can serve as one's personal military weapons. Such, in today's terms, would include rifles, shotguns, handguns, knives, and the like.
The only reason I am not out there fighting for knife carry as part of the RKBA is that I am kinda busy working to remove infringements in the RKB handguns. However, there can be no question that the knife is also an arm protected by the 2A. Because of the focus of 2A groups on firearms, we have more successfully (but not fully) protected that right, while the RKB knives has suffered near-total infringement.
It's a shame, but we have to prioritize our resources. It's still good. Once the Illinois case is upheld by the Supremes, the gun battle is all but won, with efforts now focused on shining the light of the Heller family of rulings on individual laws. That will leave more time, probably a single case, and a relatively simple argument, to get knives included in all three ruling.
In the interim, I am wholly on the side of those who would fight for the RKB knives. I just have a different focus at the moment.