Objective To analyze the type and contents of collagen protein in the organic principle of calcified cartilage zone

and the contents of hydroxyapatite in its inorganic composition.  Methods The normal human condyles of femur (n=20) from tissue bank were donated by the residents of Chongqing city. Their paraffin-embedded sections were prepared after fixation and decalcification. The type of collagen protein in the organic principle of calcified cartilage zone was qualitatively analyzed with the Picrosirius-polarization method and collagen Ⅱ protein with immunohistochemistry analysis

and the contents of collagen protein and hydroxyapatite were quantitatively analyzed with amino acid analysis and X-ray diffraction.  Results Same as hyaline cartilage

the calcified cartilage was stained light flavo-green and weak double refraction by the Picrosirius-polarization method. In the immunohistochemistry analysis of collagen Ⅱ protein

the calcified cartilage was stained strong green fluorescence and the collagen protein parallelled in joint surface near the tidemark. The content of collagen Ⅱ protein was (20.16%±0.96%) of tissue dry weight by amino acid analysis

and that of the hydroxyapatite was (65.09%±2.31%) of the inorganic composition in calcified cartilage.  Conclusion The calcified cartilage zone locates between the hyaline cartilage zone and subchondral bone in the complex tissues of articular cartilage and is mainly composed of collagen Ⅱ protein and hydroxyapatite.