A knee joint orthosis comprising a femur brace, a tibia brace, and an adjusting mechanism (31 and 32). The adjusting mechanism (31 and 32) allows the knee joint orthosis to be in a first state. With the knee joint orthosis in the first state, the femur brace encumbers the thigh, the tibia brace encumbers the lower leg, the femur brace exerts onto the thigh a force that runs along a femoral mechanical axis and away from the lower leg, and the tibia brace exerts onto the lower leg a force that runs along a tibial mechanical axis and away from the thigh. The adjusting mechanism (31 and 32) also allows the knee joint orthosis to be in a second state. With the knee joint orthosis in the second state, the femur brace does not exert onto the thigh the force that runs along the femoral mechanical axis and away from the lower leg, and the tibia brace does not exert onto the lower leg the force that runs along the tibial mechanical axis and away from the thigh, and, the femur brace disencumbers the thigh while the tibia brace disencumbers the lower leg. The knee joint orthosis is driven by a lower limb of the human body and is capable of implementing automatic transformations from the second state to the first state and subsequently from the first state to the second state that match with gaits of the human body.La présente invention concerne une orthèse darticulation du genou comportant un support fémoral, un support tibial, et un mécanisme dajustement (31, 32). Le mécanisme dajustement (31, 32) permet à lorthèse darticulation du genou dêtre dans un premier état. Lors que lorthèse darticulation du genou dêtre dans un premier état lorthèse darticulation du genou se trouve dans le premier état, le support fémoral bloque la cuisse, le support tibial bloque la jambe inférieure, le support fémoral exerce sur la cuisse une force qui circule selon laxe mécanique du fémur en séloignant de la jambe inférieure, et le support tibial exerce sur la jambe inférieure une force qui circule
