Cindy Boer

24 | Chapter 1.1 ▲ Figure 6: Risk factors and phenotypes for osteoarthritis . Osteoarthritis is a complex disease determined by genetic risk factors and environmental risk fac- tors. Several known types of genetic risk factors and environmental risk factors are given in the figure. Endophenotypes are intermediary phenotypes that are more closely associated to the underlying genetic risk factors than to the disease. osteoarthritis. Examples are the shape of the joint and the amount (thickness) of the cartilage present in the joint. In contrast to endophenotypes, Stratified phenotypes aim to differentiate subgroups within the diagnosis of osteoarthritis to reduce the heterogeneity of the osteoarthritis diagnosis, for example by grouping osteoarthritis patients based on the underlying different aetiologies, dif- ferent structural pathologies (osteophytes, joint space narrowing and lesions), amount of pain experienced or by the amount of function of the joint (mobility, range of motion).