A repeatable alignment method and local coordinate description for knee joint testing and kinematic measurement

A method for aligning cadaver knee specimens to a mechanical testing rig and determining local anatomical coordinate systems using landmarks identifiable on plane X-rays is introduced. Three sequential rotational alignments are used to position the femur and tibia relative to the coordinate system of the testing mechanism. To validate this methodology five independent observers aligned the same knee specimen. The maximum error in the alignment orientations of the tibia and femur was 2.2° from the mean. These small misalignments produced variations of up to 4.7° in tibio-femoral rotations measured during knee flexion. Kinematic measurements of 15 specimens aligned using this procedure indicate that knee alignment is reproducible and physiologically relevant.