Under the Knife 

This phrase is often used to describe a surgery or sugerical process. Knife standing for “surgery” was first recorded in 1880.
Example:

Sam: "When do you go under the knife?

Tim: "I have surgery next Wednesday. I have to take an

Ativan before I get there."

Under the Knife by SigmaNutz December 27, 2011

going under the knife 

Another saying for surgery

"Jose, I'm so nervious about your brain condition, I think you'll have to go under the knife."

going under the knife by Ross March 28, 2005

gone under the knife 

Shaved the pubic region with 1) a razor 2)brother's electric razor 3) dad's electric razor

Brian Keehner told us he went under the knife... but *someone* else hasn't... hmmmm

gone under the knife by Angie Groves January 8, 2004