Can you put knives in the dishwasher?

Three separate things go wrong. The edge knocks against racks and other items during the cycle and rolls or chips microscopically, which is what dulls it. Alkaline detergent pits high-carbon steel and can leave permanent staining. And the heated dry cycle expands and contracts wooden and composite handles at a different rate from the tang, loosening the rivets over time. A good knife washed by hand keeps its edge for years longer. Cheap stainless steak knives are a different matter and survive it well enough.

What goes wrong

• Edges chip against racks and neighbouring items.
• Detergent pits and stains carbon steel.
• Handles loosen and crack from repeated heat cycling.
• Blades pointing up in a cutlery basket are a genuine injury risk when unloading.

What to do instead

• Wash by hand immediately after use, dry at once, and store on a magnetic strip or block.

Other "can you dishwasher" questions

• Can you put cast iron in the dishwasher? No — No. Dishwasher detergent strips the seasoning and the pan rusts within hours.
• Can you put non-stick pans in the dishwasher? It depends — Only if the maker says so, and it still shortens the coating life considerably.
• Can you put an insulated bottle in the dishwasher? It depends — Only if it says dishwasher safe. Older vacuum flasks can lose their vacuum and stop insulating.
• Can you put wooden spoons in the dishwasher? No — No. Prolonged soaking and heat raise the grain, then crack and split the wood.