A medical device (115) for implanting in a knee joint of a human patient, wherein said medical device comprises an external surface (131), which is curved, which creates a curved external surface along a longitudinal axis (132 ) frontal to dorsal curve following the curved external surface, which has a central section, when said medical device is implanted in a functional position in the knee joint, where said central section is placed in the middle of said curved external surface at along said longitudinal axis, wherein said medical device comprises: - a tightly shaped structure that encircles the distal portion of the femoral bone, - at least one piece beyond, extending from the peripheral part of the curved outer surface beyond the equatorial plane of an equatorial half of the condyle, moving away from the contact surface, on at least one condyle, on at least a part of the curved outer surface, in which said first piece beyond is adapted to have the shortest distance (185) to a central axis (184) of the elongated distribution of the femur (102), which is less than the shortest distance ( 186) of a point of the maximum diameter of the femoral condyle, where the piece beyond is further adapted to create a more stable position of the medical device, when mounted on at least one of the femoral condyles, when implanted in a functional position in the knee joint, and - a fixation element pierced (150) in the at least one piece beyond, adapted to move from the front of said medical device located in the front part of the femoral bone, through the femur and inside the back of the medical device located at the back of the femoral bone, to fix the medical device by wrapping the distal portion of the femoral bone through the element fixation through, when mounted on the knee joint, characterized in that - at least two pieces (119a, 119b) are adapted to be connected to each other after implantation in the knee joint of the human patient, where The two pieces are assembled wi
