have one's legs/feet/knees cut out from under (one)
idiomDefinition of have one's legs/feet/knees cut out from under (one)
: be knocked down by something that hits one's legs very hard
When I learned that I was seriously ill, I felt as if my feet were cut out from under me.
—often used figuratively. When the program lost the grant its financial legs had been cut out from under it.