Knight will join the corporate comms and PA consultancy in January, following two years at the health standards watchdog.
She will advise Media Strategy clients including the American Pharmaceutical Group, which champions US drug firms' contribution to Britain's healthcare system.
Knight has had PR and PA responsibilities during her stint at the Healthcare Commission, providing briefings on health regulations and political issues. Previously, she was senior parliamentary officer at the Royal College of Nursing.
Knight will report to Andrew Harrison, director and head of healthcare at Media Strategy, as account director. She will also work with clients such as medical device company Deltex Medical.
Harrison said Knight's understanding of the NHS was ‘hard to beat'.