There are Critical Elements of Combative Knife Design that are universal to all knives intended for combative application. These are design elements which can determine the effectiveness of the weapon and as such require serious considerations both by the knifemaker and the eventual user.
The first Critical Elements of Combative Knife Design is the grip. It needs to be ergonomic, like it was shaped to fit your hand, it should feel at home when you pick it up. It should be comfortable, not poking any part of your hand even when you squeeze it hard. It should feel grippy like it won’t slide or slip once you close your grip around it.
The material the handle is constructed out of can vary. Common materials like G10, Micarta and other synthetics offer durability and ease of construction. Cord wraps, particularly Japanese Tsuka-Maki styles are very popular, and are somewhat battle proven despite their low-tech and primitive appearance. Care should be given to materials like wood and other natural materials like bone. While these can be extremely appealing, highly polished materials, which traditionally these materials tend to be, can also become slick and slippery when wet. If constructed properly however, they should perform just as well as anything else.
Irrespective of what the handle material is however, a handle design can be made or broken by its actual form. If the handle form is flawed, nothing will make it a perfect fit for the hand. The natural form is everything. For me personally I go an extra few steps, by adding that I don’t want any excess handle protruding from my grip, I want it nice and clean to reduce snagging and make stripping actions cleaner. I also don’t want anything that spreads my fingers, like multiple finger grooves or choils. A combative knife should also have a handle design that lends itself to accessing from concealment. The handle design should allow the user to index it perfectly on the draw, to minimize the amount of adjustment that needs to be made in the hand in order to get the knife comfortable – it should be comfortable right out of the sheath.
Lastly, and this is very specific to me personally, I don’t like finger rings.
There are styles out there that make use of them, like those who practice Karambit and it’s fine if that’s how you are trained, but for me they can spread load onto the ring finger if not done properly, and also have the ability to quickly become a finger trap if things get a little difficult, as they tend to do in realistic dynamic encounters.
Sometimes the best solutions are to keep things simple and practical, it doesn’t mean you can’t make things look good, but function and form need to come together as one. The spiritual union that can make practicality a thing of beauty.