Cooked chicken bones are bad for dogs to ingest because the bones may splinter and puncture the intestines during digestion. Dogs that swallow large chunks of chicken bones could end up with a blockage in the intestines.
Bones that puncture the intestines or abdominal wall can cause internal bleeding and infection. This can be fatal and thus requires emergency veterinary treatment. Larger pieces that cause a blockage will trap waste material and gas, causing pain and possible blood toxicity.
If a dog accidentally ingests chicken bones, signs of a problem include diarrhea, vomiting, apparent pain in the abdomen, and rectal bleeding. Many dogs that accidentally ingest chicken bones do fine. However, dog owners should avoid purposely feeding their dogs chicken bones.