Device for protecting the knee joint that is able to engage with a ski boot

A device for protecting the knee joint of a skier, the device being for installing on a ski boot having a footwear portion surmounted by a collar, the device having first connection means designed to be fastened to the collar of the boot and a rigid shell designed to cover the front of the tibia of the skier, at least in part, the shell extending between a high portion for being situated level with the skier's knee and a low portion covering a portion of the collar of the boot, the shell including or supporting, on its high portion, rigid lateral flanges suitable for being put into contact with the knee on either side of the knee, being in contact at least with the condyles of the femur of the skier, the low portion of the shell being designed to cover part of the collar of the boot and including second connection means complementary to the first connection means of the collar of the boot and suitable for securing the shell to and above the collar of the boot in such a manner that the association of the first and second connection means provides a connection with limitation of movement in rotation of the shell relative to the boot about an axis of rotation substantially parallel to the axis of the collar of the boot.