COL9A1 and osteoarthritis: In a cartilage disease condition, such as rheumatoid arthritis or osteoarthritis, there is a significant shift in interactivity, with Col2A1 interacting solely with Col10A1, without any interaction with Col1A2, Col9A1 and 2, and Col11A1 and 2, leading to poor cartilage formation and abnormal composition [104,105].