Collagen of human articular and costal cartilage

Collagen comprises approximately 90 per cent of the protein of human articular cartilage. Only about 1 per cent of the total collagen could be extracted by solutions of 5 M guanidine‐HCl from normal cartilage, and the extractability of collagen from fibrillated specimens was not elevated. In costal cartilage, the proportion of noncollagenous protein increases almost threefold during skeletal growth. Moreover, the extractability of costal cartilage collagen decreases as a function of age.