To a large extent it depends what type of knife you're talking about.
Many/most ceramic knives will still contain sufficient metal to trigger a metal detector. In the case of "pocket knife" style knives, this will normally be in the body of the knife. For kitchen knives there will often be metal in the handle of the knife, and/or in the clips/screws/etc that hold the handle on.
For knives that are made completely of ceramics, or contain handles without metal, then it's a different story. In general, these will not be detected by standard metal detectors, and this is one of the main reasons that more and more countries are starting to use various forms of millimeter wave scanning devices as they will detect non-metallic items as well.
For locations still using standard metal detector machines, many will also configure the machine to randomly select people for further scrutiny. For example, in the US where metal detectors are generally only used for Pre-Check passengers, a random number of people going through the metal detector will be randomly selected by the metal detector and will have to either go through the millimeter wave scanner, or receive a pat-down check.
Whilst this will not detect every person attempting to smuggle something like a ceramic knife though, it's intended as being a great enough risk to someone attempting to do so that they will avoid doing it in the first place.
One way or another, if you are caught carrying something like this through an airport metal detector then odds are... well.. lets just say that you're probably going to be missing your flight...