Structural component of hyaline cartilage and vitreous of the eye. Heterotrimer of an alpha 1(IX), an alpha 2(IX) and an alpha 3(IX) chain (By similarity). The chains are linked to each other by interchain disulfide bonds (By similarity). Trimers are also cross-linked via hydroxylysines (By similarity). Covalently linked to the telopeptides of type II collagen by lysine-derived cross-links. Prolines at the third position of the tripeptide repeating unit (G-X-Y) are hydroxylated in some or all of the chains. Belongs to the fibril-associated collagens with interrupted helices (FACIT) family.