The principal stresses and their path line, normal stresses, contact stresses between patella and ossis femoris were determined in various flexion angles (15°, 30°, 45°, 60°, 75°, 90°). Two of the correlations were:
(1) Maximum principal stress in the front of patella
(2) Maximum contact stress between patella and ossis femoris
where W was body weight subjected by a single foot.
It was proved that the transverse break of patella resulted from the case that the principal stress in the front of patella exceeded ultimate tensile strength. And Tension Band Wiring (TBW) therapy conformed to the law of physiological stress field. A modified K-needles position in TBW therapy was suggested. These results are useful for further research of human patella mechanics and recovery therapy. No similar result has been found in American MEDLIN Data Bank.