The short answer:
The apparently maniacal and cruel person breaks someone’s bone after strapping them down to a table and rendering them helpless, makes deep disfiguring cuts through the skin, fat, and muscle, tears away critical ligaments and tendons, chops off sections of bone, cuts blood vessels and causes a great deal of bleeding.
Then he sews the tendons on to a new location, sews together all the cuts, stops the bleeding, puts dressings and salves on the wound, gives medicine to heal, and to relieve the pain, comes and visits every day to see what he can do to help, and to bring good cheer.
When you have become a new person, who can get out of the wheelchair for the first time in your life, are you grateful to the doctor?