Abnormal morphology of collagen fibers in cartilage. In cartilage, collagen II, actually a collagen II:IX:XI heterofibril, is by far the most important type of collagen. A number of abnormalities may be appreciated by electron micrography or biochemical investigations, including sparse collagen fibers in the cartilage matrix. The phenotype is Abnormal cartilage collagen (HP_0008271, a Human Phenotype Ontology entry).