Editing Cartilage (section)

=== Articular cartilage ===
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[[File:Cartilage from mouse joint.jpg|thumb|Section from mouse joint showing cartilage (purple)]]

The articular cartilage function is dependent on the molecular composition of the [[extracellular matrix]] (ECM). The ECM consists mainly of [[proteoglycan]] and [[collagen]]s. The main proteoglycan in cartilage is aggrecan, which, as its name suggests, forms large aggregates with [[hyaluronan]] and with itself.<ref name="Chremos2023">{{cite journal | vauthors = Chremos A, Horkay F | title = Coexistence of Crumpling and Flat Sheet Conformations in Two-Dimensional Polymer Networks: An Understanding of Aggrecan Self-Assembly | journal = Physical Review Letters | volume = 131 | pages = 138101  | date = September 2023 | issue = 13 | doi = 10.1103/PhysRevLett.131.138101 | pmid = 37832020 | bibcode = 2023PhRvL.131m8101C | s2cid = 263252529 }}</ref> These aggregates are negatively charged and hold water in the tissue. The collagen, mostly collagen type II, constrains the proteoglycans. The ECM responds to tensile and compressive forces that are experienced by the cartilage.<ref>{{cite journal | vauthors = Asanbaeva A, Tam J, Schumacher BL, Klisch SM, Masuda K, Sah RL | title = Articular cartilage tensile integrity: modulation by matrix depletion is maturation-dependent | journal = Archives of Biochemistry and Biophysics | volume = 474 | issue = 1 | pages = 175–82 | date = June 2008 | pmid = 18394422 | pmc = 2440786 | doi = 10.1016/j.abb.2008.03.012 }}</ref> Cartilage growth thus refers to the matrix deposition, but can also refer to both the growth and remodeling of the extracellular matrix. Due to the great stress on the patellofemoral joint during resisted knee extension, the articular cartilage of the patella is among the thickest in the human body. The ECM of articular cartilage is classified into three regions: the pericellular matrix, the [[territorial matrix]], and the interterritorial matrix.