Aggrecan, a proteoglycan, is a key component of cartilage structure and the function of joints. It provides articular cartilage with structural support and load-bearing properties through facilitated hyaluronan interactions that form stable ternary complexes in the extracellular matrix. Crucial to chondro-skeletal morphogenesis during fetal development, the structural motif of aggrecan is similar to that of a link protein, as it is composed of three globular domains - G1, G2, and G3 - and a large extended region to allow for glycosaminoglycan attachment. The three globular domains are involved in aggregation, hyaluronan binding, cell adhesion, and chondrocyte apoptosis. Faults in functional properties of aggrecan are involved with many cellular pathways involving degenerative joint and bone diseases, including osteoarthritis, spinal, cranial, and epi-/metaphyseal abnormalities.

Aggrecan has been identified by Western blot and similar electrophoretic techniques and analyzed with RT-PCR. Related assays include those associated with hyaluronan binding or immunostaining to assess collagen potential.