Type II collagen is the main collagen in joint cartilage, forming the fibre network that gives cartilage its strength. In adults it is replaced very slowly.
Also called collagen II, CII, COL2A1 (its gene).
Collagen makes up two-thirds of the dry mass of adult joint cartilage, and type II collagen is its principal molecule, woven with smaller amounts of collagens IX, XI and others (Eyre 2002). Each molecule is a triple helix of three protein strands (Mitchell 1996).
It lasts a very long time. Its half-life has been estimated at 117 years, against 15 for skin collagen (Verzijl 2000), and radiocarbon dating found virtually no replacement after the skeleton stops growing (Heinemeier 2016). That is why its loss is considered irreversible, unlike the loss of aggrecan (Li 2011). One group has argued for more turnover than that, finding it highest in ankle cartilage (Hsueh 2019).
MMP13 has the highest activity against it of any collagenase (Li 2011). Its breakdown fragments, such as CTX-II, are measured in blood and urine as markers (Abo-Zalam 2025; Kumar 2025).
Type II collagen is the main collagen in joint cartilage. Collagen makes up about two-thirds of adult cartilage's dry mass, and type II is its principal molecule, woven...
Its collagen barely does, on most measurements. Radiocarbon dating of knee cartilage from 23 people found virtually no replacement of the collagen network after the...
It depends which part is damaged. Reviews describe losing aggrecan, the water-holding molecule in cartilage, as an early and reversible step, and losing type II collagen...