Collagen II, also known as type II collagen, is a fibrillar collagen that plays a crucial role in the structure and function of various tissues, particularly in cartilage. It is the main fibrillar collagen of growth plate cartilage and other cartilages, accounting for 95% of the collagens and approximately 60% of the dry weight of cartilage. Collagen II is not only found in cartilage but also in the vitreous humor, intervertebral disks, and inner ear. It is important for the normal development of embryonic bone, linear growth, and the ability of cartilage to resist pressure. Mutations in Collagen II can result in several types of chondrodysplasia, leading to premature osteoarthritis. It is also associated with diseases like Stickler syndrome, Wagner syndrome, and Kniest dysplasia, which can affect the vitreous and other connective tissues.