Ceramic knives and airport (or any other) security

I ran into this question that discussed putting a ceramic knife in the carry-on luggage. Clearly that won't work, as the carry-on luggage goes through the x-ray machine and ceramics in general have rather high density, so would certainly show up on the x-ray image.
However ceramic knife has no metal content. So what would prevent somebody from putting it in their pocket and simply walking through the security? Obviously, one would need to ensure that they have nothing else on them that would trigger the metal detector (e.g. coins, keys, etc.) to avoid the secondary pat down.
Specifically the question is about how do airport security ensure that travellers do not carry ceramic knives onto flights, short of physical pat down of everybody or using new technologies, such as millimetre x-ray?
Pictures about "Ceramic knives and airport (or any other) security"



Can ceramic be seen on xray?
But ceramic becomes brightly illuminated under T-ray light and is easily detected, even through several layers of clothing or the sole of a shoe.Are knives TSA approved?
Can I bring a knife in my carry-on? You are NOT allowed to bring a knife in your carry-on except for \u201cplastic or round-bladed butter knives.\u201d What is a TSA approved knife? There are no TSA approved knives except fo \u201cplastic or round-bladed butter knives.\u201dCan you bring a knife in checked luggage?
Checked Bags: YesExcept for plastic or round bladed butter knives. Any sharp objects in checked bags should be sheathed or securely wrapped to prevent injury to baggage handlers and inspectors.Can I bring a knife on a plane?
According to the TSA, you can bring any type of knife in your checked luggage, including death stars, swiss army knives, and even swords. TSA doesn't limit the blade length, curved blades, concealed blades, or anything of that kind.The Science of Airport Security
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Matthew Turner, Ketut Subiyanto, Ketut Subiyanto, Ketut Subiyanto