1. A method of determining a reference point on condyles of a femur using a computer assisted surgery system, the method comprising: providing a digitizer having a trackable member which is locatable and trackable in three dimensional space by the computer assisted surgery system, the digitizer including perpendicular first and second planar surfaces against which condylar surfaces may be abutted; creating a digitized plane using the digitizer by abutting the first planar surface of the digitizer directly against posterior surfaces of the condyles and abutting the second planar surface directly against distal surfaces of the condyles, the digitized plane being at least one of a posterior plane and a distal plane of the condyles, the posterior plane and the distal plane being respectively defined by said first planar surface of the digitizer abutted against the posterior surfaces of the condyles and said second planar surface of the digitizer abutted against the distal surfaces of the condyles; and determining a location of the reference point in the digitized plane. using the computer assisted surgical system, the reference point being a most remote point of the femur within said digitized plane.