Potential negative modulator of chondrocyte differentiation. Inhibits collagen fibrillogenesis in vitro. May influence chondrocyte's differentiation by acting on its cellular collagenous microenvironment. Associates with collagen and binds to collagen fibrils. Expressed in cartilage, including articular knee cartilage, where it localizes to the extracellular space in the area immediately surrounding the chondrocytes, not detected in any other tissues (at protein level). Not detected before 13.5 dpc. From 13.5 dpc on, prominently expressed only in mesenchymal condensations and in cartilaginous tissues. In the ATDC5 cell line model, up-regulated during chondrocyte differentiation, absent in precondrogenic, non-differentiating stage (at protein level). Belongs to the small leucine-rich proteoglycan (SLRP) family. SLRP class IV subfamily.