May play a role in cartilage scaffolding. Expressed in articulated and meniscal cartilage (at protein level). Also detected in heart, skeletal muscle and brain. Not detected in growth plate cartilage. In the knee joint, detected in articular cartilage from 2 weeks of age but not at earlier stages (at protein level). Initially localizes to the surface zone of articular cartilage but by maturity (8 weeks) is found in the intermediate to deep zones (at protein level). May be cleaved into 2 chains possibly by a furin-like protease upon or preceding secretion. N-glycosylated.