System for determining the position of a knee prosthesis

The method of claim 4, further comprising the steps of:

• using the computer, determining an intersection contour between a surface of the 3D computer model and at least one of a distal section plane of the femur and a tibial section plane of the tibia;
• and
• displaying the intersection contour on the display.

The method of claim 4, wherein the first bone is the femur and the method further comprises the steps of:

• attaching a second locatable element to a patella;
• and
• using the computer, measuring a trajectory of the patella relative to the femur while the knee joint moves between flexion and extension, and determining the position of the femoral component on the 3D computer model based upon the measured trajectory of the patella.

The method of claim 4, further comprising the step of displaying at least one of a distal section plane of the femur and a tibial section plane of the tibia on the display.

The method of claim 4, wherein the first bone is the femur and the method further comprises the steps of:

• determining a most distal point on the femur and a most posterior point on the femur;
• and
• using the computer, calculating a position of a distal section plane, wherein the position is a distance from the most distal point equal to a first predetermined position, calculating a position of a posterior section plane, wherein the position is a distance from the most posterior point equal to a second predetermined position, and calculating a size of a femoral component to be implanted based on the calculated position of the distal section plane and the posterior section plane.