Immunohistochemical collagen analysis of the most superficial layer in adult articular cartilage

We investigated immunohistochemically the collagen type of the most superficial layer in 10 normal adult human articular cartilage specimens obtained from eight femoral heads and one each of the femoral condyle and the talus using routine light microscopy and polarizing microscopy. A membrane-like structure with strong bire-fringence covering the articular surface was observed under polarizing microscopy in each specimen. This structure was stained with anti-type I and anti-type III collagen antibodies but not with anti-type II collagen antibody. This immunohistochemical finding was identical to that in synovial tissue. The results of this study confirm that the most superficial layer of adult normal articular cartilage consists not of type II collagen but of types I and III, and that this layer is absolutely independent from its deeper layer.