Recently, my mother-in-law was reading an Amanda Pig book with my daughter. Anna paused at the word “know,” and my mother-in-law laughingly said, “Oh, that word is /cuh-no/!” — making a joke by suggesting that the in the word is actually voiced, or articulated. Anna thought that was very funny, and proceeded to find and read several more examples within the book (“cuh-nee” for knee) (“cuh-nocked” for knocked). It turned into a sort of cute word search.
So, what is the origin of the in the cluster? According to Richard Venezky’s book The American Way of Spelling (a good book for those interested in the structure and origins of American English orthography), the was little used in Old English, and some time in the middle of the 17th century, /kn/ was leveled to /n/. And there you have it. You “cuh-no?”