The 24-year-old, who was looking to close in on Chemmy Alcott’s record of seven ladies national titles, has been ruled out for up to four weeks.
Brown had been in good form, defending her super G title in Tignes on Sunday.
“It is my own fault, you are meant to move forward over jumps and I went backwards,” said Brown.
She added: “It is a shame to finish on a low since yesterday was a high. It is not a happy knee at the moment, it is getting very swollen in size.”
The biggest competition in British Alpine skiing takes places from 25 March to 6 April in the French Alps.