Figure 1.

Survey of the most abundant glycosaminoglycans (GAGs) of healthy hyaline articular cartilage. As schematically shown, chrondroitin sulfate (CS, green colored) chains are more abundant than keratan sulfate (KS, purple colored) chains. Hyaluronic acid (HA, red colored), also named hyaluronan, functions as the backbone in the so-called “bottle-brush” structure. Structural changes in GAGs may lead to the degradation of the cartilage and thus to function loss of the cartilage. Characteristic patterns of healthy, rheumatoid arthritis (RA) as well as osteoarthritis (OA) cartilage are illustrated using stock photos from the illustration platform Colorbox (reproduced with permission using the campus license from Leipzig University).