Patent ID: 7351263

Claim:
Complete knee prosthesis, comprising: a femoral element ( 1 ) with femoral condyles ( 3 ) having, seen in the sagittal plane, a spiral form corresponding substantially to a form of natural condyles, with gradual reduction of their radii towards posterior sectors, and comprising a medial lobe ( 6 ) with a curved surface; a tibial seat forming an upper support plate, and a medial plateau ( 2 ) intended for resting against said upper support plate of the tibial seat and comprising glenoid cavities ( 2 b ) receiving the condyles ( 3 ) of the femoral element ( 1 ), said medial plateau ( 2 ) having a medial prominence ( 5 ) which forms a posterior support surface ( 5 a ), against which said lobe ( 6 ) is capable of resting during the movement of the joint, wherein, the glenoid cavities ( 2 b ) of the medial plateau ( 2 ) and the condyles ( 3 ) of the femoral element ( 1 ) are formed to be congruent when the prosthesis is in extension and on a first part of the flexion movement of the joint extending between this extension position and the angle of flexion between about 30 to 80° from which the congruence of the condyles ( 3 ) with the glenoid surfaces is lost due to the spiral form of the condyles ( 3 ), the posterior sectors of the condyles ( 3 ) and of the medial lobe ( 6 ) inscribe circles of same centers, the medial lobe ( 6 ) is formed so as not to contact said posterior support surface ( 5 a ) during said first part of movement, but to contact said posterior support surface ( 5 a ) when said flexion angle is reached and then to carry the joint against this posterior support surface ( 5 a ) over the remainder of the flexion travel, while performing a rolling movement of the femoral condyles ( 3 ) with respect to the tibial seat in the posterior direction, called “roll-back”, and said posterior support surface ( 5 a ) has a curved shape corresponding to the curved shape of said medial lobe ( 6 ), so that this lobe rests against this posterior support surface ( 5 a ) over a wide surface throughout the second part of movement, consecutive to said first part of movement.