Collagen-binding adhesin that mediates bacterial adherence to collagenous tissues such as cartilage (PubMed:8218209). Participates in the infectious process by acting as a virulence factor in many different animal models of staphylococcal infections including arthritis, endocarditis and keratitis (PubMed:10816547, PubMed:15181582). Inhibits the activation of the classical complement pathway by interacting with host C1q and interfering with the association between host C1r with C1q (PubMed:23720782). Interacts (via N-terminus) with type I collagen (PubMed:16362049). Interacts with host C1QA (PubMed:23720782). Composed of a N-terminal A-region and a number of B-repeats depending on the strain. At the C-terminal end are features required for surface targeting and covalently anchoring to the peptidoglycan. The collagen binding activity is located in the A-region.