This report demonstrated definitively that chondroadherin binds to CII. Furthermore, based on extraction from biological materials, and the intactness of the extracted complexes, this report provided strong evidence that binding may also occur in vivo. The most significant implication from this study is that as chondroadherin is a territorial component, its binding to CII suggests that this complex may have cell regulatory function, in addition to structural functions. The cell regulatory function may be mediated by the complexes in association with a2-?1 integrins that are expressed on the cell surface of chondrocytes. Chondroadherin is localized in a restrictive manner in the late proliferative cells of the growth plate, and to the developing articular cartilage (see Additional information [1]). This further suggests that the interactions between chondroadherin and collagen may regulate chondrocyte growth and proliferation. In addition to chondroadherin, several other LRR proteins are also bound to collagen fibrils. Targeted disruption of biglycan in mice leads to loss of integrity of the collagen network and an osteoporosis-like phenotype (see Additional information [2]). Altered levels of biglycan, decorin and fibromodulin were detected in an experimental osteoarthritic model (see Additional information [3]). Therefore, another significant implication from the current study is that chondroadherin contributes to the integrity of collagen network by regulating the assembly. Deregulation of chondroadherin may then lead to congenital skeletal disorder, or cartilage degenerative diseases such as arthritis. The biochemical interactions of chondroadherin and collagen may represent yet another mechanism for collagen homeostasis.