The first two are bad situations, and the latter is good. How to judge depends on the position of the buried knife in the house and the orientation of the back of the knife.
I don't know if your family has invited people to see Feng Shui. If so, it is probably the third kind, which is very good. If you have enemies in your family, they are the first two evils.
If it has nothing to do with your family and your neighbors, it doesn't matter much.
Anyway, personally, it is always bad to have a knife at home. It's best to dig it out and take it away. As for some experts, hanging the Eight Diagrams Mirror is also a helpless game that can't be dug away.