He immediately entered private practice in Naperville, but served as a lieutenant in the United States Army infantry during World War I, from 1917 to 1919.
He then returned to private practice until 1930, also serving as an assistant state's attorney of DuPage County, Illinois from 1922 to 1930.
He was a Judge in DuPage County from 1930 to 1939, and on the 16th Judicial Circuit Court of Illinois from 1939 to 1953.
He was confirmed by the United States Senate on May 13, 1953, and received his commission the next day.
[1] Knoch was nominated by President Eisenhower on August 16, 1958, to a seat on the United States Court of Appeals for the Seventh Circuit vacated by Judge Walter C. Lindley.