Collagen type II, the most abundant structural component of cartilage, has an estimated halflife of 2420 days (6.6 years) . Over time, glycyl radicals form in AKU cartilage, enabled by initial, low-level HGA radical formation. Once formed, such glycyl radicals can oxidize nearby HGA molecules, and the process can be self-perpetuating, whereby increased oxidation of HGA in cartilage, further pigment formation, and further collagen damage can occur.