External Knee Geometry Surface Variation as a Function of Subject Anthropometry and Flexion Angle for Human and Surrogate Subjects

The current study was designed to compare the surface anatomy of the knee for different human subject anthropometries using a 3-D, non-contact digitizer which converted the anatomy into point clouds. The subjects were studied at flexion angles of 60, 90, and 120 degrees. Multiple subjects fitting narrow anthropometrical specifications were studied: 5^th percentile female, 50^th percentile male, and 95^th percentile male. These data were then compared to a corresponding anthropometrical crash dummy knee which served as an unambiguous control. Intersubject human comparisons showed surface geometry variations which were an order of magnitude smaller than comparisons between the human and dummy knee. Large errors between the human and dummy were associated with the muscle bulk proximal and distal to the popliteal region and the rounder shape of the human knee. These data indicate that pair matching for human height and weight yields similar knee surface anatomies while there are significant variations between the human and corresponding dummy knees.