Under the knife.
Under the knife.
When someone is 'Under the knife', they are literally undergoing surgery. The 'knife' represents the surgeon’s scalpel, and the phrase highlights the serious nature of the process. It is used to describe the critical and vulnerable condition of being operated on.
He went under the knife for heart surgery.
He had surgery on his heart.
She had to go under the knife to remove her appendix.
She had surgery to remove her appendix.
Under the knife, doctors worked to save his life.
The doctors performed surgery to save his life.