A medical device for implantation in a knee joint of a human patient, said medical device having an outer surface, being curved, creating a curved outer surface along a frontal to dorsal curved length axis following the curved outer surface, having a middle section, when said medical device is implanted in a functional position in the knee joint, said middle section being placed in the middle of said curved outer surface along said length axis, said medical device comprising: - a form fitted structure clasping the distal portion of the femoral bone, - at least one beyond part, extending from the surrounding part of the curved outer surface beyond an equatorial plane of an equatorial half of the condyle, extending away from the contacting surface, on at least one condyle, on at least a part of the curved outer surface, wherein the at least one first beyond part is adapted to have a closest distance to a centre axis of the elongated distribution of the femur, being smaller than the closest distance of a point of the maximum diameter of the femoral condyle, the beyond part further being 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 through-going fixation element in the at least one beyond part, adapted to travel from the frontal part of said medical device positioned at the frontal part of the femoral bone, through the femoral bone and into the rear part of the medical device positioned on the rear part of the femoral bone, to fixate the medical device clasping the distal portion of the femoral bone by the through-going fixation element, when mounted in the knee joint, characterized in that - at least two parts (119a, 119b) are adapted to be connected to each other after implantation in the knee joint of the human patient, wherein the two parts is mounted with a form fitted structure (137, 138) along a length axis of the medical device along the functional movement of the knee joint. - a form fitted structure clasping the distal portion of the femoral bone, - at least one beyond part, extending from the surrounding part of the curved outer surface beyond an equatorial plane of an equatorial half of the condyle, extending away from the contacting surface, on at least one condyle, on at least a part of the curved outer surface, wherein the at least one first beyond part is adapted to have a closest distance to a centre axis of the elongated distribution of the femur, being smaller than the closest distance of a point of the maximum diameter of the femoral condyle, the beyond part further being 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 through-going fixation element in the at least one beyond part, adapted to travel from the frontal part of said medical device positioned at the frontal part of the femoral bone, through the femoral bone and into the rear part of the medical device positioned on the rear part of the femoral bone, to fixate the medical device clasping the distal portion of the femoral bone by the through-going fixation element, when mounted in the knee joint, characterized in that - at least two parts (119a, 119b) are adapted to be connected to each other after implantation in the knee joint of the human patient, wherein the two parts is mounted with a form fitted structure (137, 138) along a length axis of the medical device along the functional movement of the knee joint.