A vet will not recommend the surgical removal of a dog's limb lightly. But in some cases, amputation is the only option.
However, it’s important to remember that if your pet sustains an injury or develops a disease or infection, that doesn’t mean an amputation will happen. Typically, it’s used as a last resort to save the dog’s life and improve chronic pain.
Medical issues or conditions that may result in an amputation include:
Catastrophic injury
Certain cancers, like osteosarcoma, a bone cancer
Infection
Soft tissue damage
Frostbite
Birth defects or other abnormalities