Knowles joined Dennis this week after quitting her role as PR manager for the Cosmopolitan division of the National Magazine Company last month, after just six months.
Up until now Dennis has used agency support - most recently a three-year spell with Talk Loud, whose contract expired in April.
Knowles, who becomes PR manager in the consumer marketing department, said: 'I want to devise more creative ways to gain publicity and build on the brands.'
She said practical reasons had played a part in the in-house move, as 'being in the same building it's easier (for the PR team) to get a feel for the magazines'.
Knowles takes responsibility for consumer PR for Dennis's Maxim, Maxim Fashion, Shape and Men's Fitness titles. In addition, she is to promote car magazines EVO and Auto Express.
She added that she planned to raise the media profile of key editorial staff, such as magazine editors and fashion directors.
Knowles reports to group marketing manager (consumer) Sarah Thorne and, ultimately, to group publishing director Andy Semple.
Knowles said she had no immediate plans to boost the in-house team, but added that hiring might be possible in around a year's time.
Before Nat Mags, Knowles was events and PR manager for William Reed Publishing for almost three years.