This is a common misconception that likely stems from the fact that the female hyena's external genitalia is very similar in appearance to the male's penis. However, female hyenas have a pseudo-penis, which is a highly specialized clitoris that functions as a reproductive organ, allowing them to urinate, mate, and give birth through it.
The mating process in hyenas is quite unique, with females taking the lead in choosing their mates. While they do engage in various displays of dominance and aggression, the actual mating act is more of a cooperative process. The female hyena controls the timing of the mating event and will signal her readiness to the male.
So, to answer your question directly, hyenas do not knot during mating, and the appearance of their genitalia is simply a result of the fascinating evolutionary adaptations of these fascinating creatures.