Plays a role in the structural integrity of cartilage via its interaction with other extracellular matrix proteins such as the collagens and fibronectin (PubMed:32686688). Can mediate the interaction of chondrocytes with the cartilage extracellular matrix through interaction with cell surface integrin receptors. Could play a role in the pathogenesis of osteoarthritis. Potent suppressor of apoptosis in both primary chondrocytes and transformed cells. Suppresses apoptosis by blocking the activation of caspase-3 and by inducing the IAP family of survival proteins (BIRC3, BIRC2, BIRC5 and XIAP) (By similarity). Essential for maintaining a vascular smooth muscle cells (VSMCs) contractile/differentiated phenotype under physiological and pathological stimuli. Maintains this phenotype of VSMCs by interacting with ITGA7 (By similarity). Binds 11-14 calcium ions per subunit. Pentamer; disulfide-linked. Exists in a more compact conformation in the presence of calcium and shows a more extended conformation in the absence of calcium. Interacts with ITGB3, ITGA5 and FN1. Binding to FN1 requires the presence of divalent cations (Ca(2+), Mg(2+) or Mn(2+)). The greatest amount of binding is seen in the presence of Mn(2+). Interacts with MATN1, MATN3, MATN4 and ACAN. Binds heparin, heparan sulfate and chondroitin sulfate. EDTA dimishes significantly its binding to ACAN and abolishes its binding to MATN3, MATN4 and chondroitin sulfate. Interacts with collagen I, II and IX, and interaction with these collagens is dependent on the presence of zinc ions. Interacts with ADAMTS12 (By similarity). Interacts with ITGA7 (By similarity). Expressed in cartilage, including nasal, knee epiphyseal and rib tissues. Abundantly expressed in chondrocyte and tendon extracellular matrix (at protein level) (PubMed:32686688). In knee epiphyseal cartilage, expression is detected from 12.5 dpc onwards, with significant up-regulation at 16.5 dpc and again at postnatal day 5. Expressed at least until 10 months of age. The cell attachment motif mediates the attachment to chondrocytes. It mediates the induction of both the IAP family of survival proteins and the antiapoptotic response. The TSP C-terminal domain mediates interaction with FN1 and ACAN. Each of the eight TSP type-3 repeats binds two calcium ions. The TSP C-terminal domain binds three calcium ions. Belongs to the thrombospondin family.