Can a Knife Break Bone?

There’s a knife for nearly every task, whether they’re short, long, wide, serrated, or sharpened to the point where they can slice paper as easy as butter. Cutting or breaking bones, however, takes a different sort of knife.

Some knives can break bones, but the question is open-ended enough to allow for plenty of wriggle room, such as what kind of bones, whether the blade is being swung or merely slicing, what type of knife, and are we dealing with human or animal bones?

For the sake of not getting too morbid, we’re going to go with general animal bones to convey a much more illustrative set of examples, especially since we’re not talking human combat, field surgery, or anything else involving the necessitation of breaking or cutting through a human bone.

Knives That Can Break Bone

The bones of mammals are insanely strong, far more than you would think. For example, a cubic inch of human bone can withstand the weight of 5 pickup trucks. That’s pretty intense, and you get similar numbers with most animals who share a similar size in bones and bone density.

In other words, you’re not going to break the femur on a deer with a pocket knife. But some knives can get the job done, even when it comes to thicker bones, such as the femur.

  • Cleaver: Average weight is around 2lbs and is designed to cut through denser bones.
  • Butcherknife: One of the most recognizable knives globally, it can cut through small and medium bones.
  • Chef’s Knife: Another dominant knife in a butcher’s arsenal, it can also cut through small to medium bones. 

A knife isn’t capable of cutting through a bone, as it’s more like a driving, breaking force that is applied to something that is essentially stronger than steel. To break a bone, the knife has to either be driven in, through force or applied with a downward force, like swinging a sword. 

Exceedingly sharp instruments can cut through bones rather than smash through them. Still, it has to be a thin bone to do so without using a significant amount of force. 

Force is what the cleaver brings to the table. It is blade-heavy and weighs up to two pounds. When butchers cut through bone, they often reach for the cleaver and finish the job with a single, sweeping blow. 

When it comes to a butcher’s knife or a chef’s knife, you should only be dealing with small or medium bones. This is because the strength of these knives is in the heel, and you can’t swing them like you would a cleaver. 

Instead, these two knives require a careful placement followed by an increasing downward force until they both cut and break through the bones. However, small and medium bones will be cut at the joints for the most part. 

Outside Knives That Can Cut or Break Bone

Beyond the kitchen, several knives are designed to cut through bone. Some of them are so sharp that they literally cut far more than break the bones that they are applied to.

  • Ka-Bar
  • Machete
  • Bowie Knives
  • Kukri

Kukri blades and machetes are as close to swords as you can get without being considered a sword. However, like meat cleavers, these knives are more likely to cut through bone when used as a swinging blade rather than precision cutting. 

Bowie knives and ka-bar—if they are considerably sharp—can be used when field dressing a deer, as they are generally sharp enough and large enough to slice through the breast bone, opening up the deer and making it easier to remove the insides. 

While it’s not necessary to field dressing (you can reach up inside the deer and cut the windpipe), it is something that hunters practice here and there. But, of course, cutting through the flat sternum of a deer isn’t the same as trying to cut through a leg bone or something of similar size. 

Why is Bone So Difficult to Break or Cut?

There’s more to the bone than just a single material. They are, after all, living organism that grows, replaces lost material, and shrink in times of deprivation. There are three parts that a knife must cut or break through to separate the bone.

  • Compact Tissue
  • Cancellous Tissue
  • Bone marrow

The hardest and most dense portion of the bone is the outside layer, the compact tissue. The cancellous tissue beneath the compact tissue is softer and more fibrous but no less strong. Lastly, the bone marrow isn’t much of an obstacle for a hard swung cleaver. 

That may not sound like much in the greater scheme of things, but bones easily outclass fully cured concrete in terms of pure hardness. Despite the extreme hardness and durability of your bones, they are also flexible, which helps them absorb impacts.

Suppose the cleaver doesn’t pass all the way through. In that case, it is likely to get stuck in the spongy material within, without breaking all the way around because of that degree of flexibility. 

Ironically enough, it is not the blow of a heavy knife or a blunt instrument that has the easiest time breaking through bone, but rather, it’s the odd angles of force. The same thing that makes a bone flexible is its undoing when flexed in sudden, explosive movements.

This is especially true if there is already a great deal of weight on the bone. Travelling in one direction and suddenly changing to another with explosive force is more than enough to snap a bone in two or at least fracture it to a degree. 

Final Thoughts

There are a few knives out there capable of striking bones and either breaking them or cutting through. Some are kind of in between, slicing enough of the way into the bone to weaken it enough to break.

However, these knives are few and far between and are generally speciality knives. Most knives, such as pocket knives, buck knives, and even swiss army knives, have many purposes but cutting through bone simply isn’t one of them. 

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Knives are useful tools for many tasks, even as weapons if need be; however, are they capable of cutting through bone?


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