The invention relates to a device for protecting the
knee joint of a skier (S), said device being intended to be fitted on a ski boot (2) comprising a footwear part surmounted by a
cuff (21), the device comprising first connecting means (22a, 22b, 23) intended to be fixed to the
cuff (21) of the boot (2) and a shell (10) intended to at least partially cover the front of the
tibia (T) of the skier (S), this shell (10) extending between a top part (11) intended to be located in the region of the skier's knee and a bottom part (12) that covers a portion of the
cuff (21) of the boot (2), the shell (10) supporting, on its top part (11), lateral flanges (11a, 11b) that are able to be brought into contact with the knee on either side of the knee, being at the least in contact with the
femoral condyles (CF) of the skier (S), the bottom part (12) of the shell (10); being intended to partially cover the cuff (21) of the boot (2) and comprising second connecting means (12a, 12b) complementary to the first connecting means (22a, 22b) of the cuff (21) of the boot (2) in order to be secured to the cuff (21) of the boot (2).