Osteoarthritis (OA) is the most frequent cause of rheumatic complaints. OA is a group of distinct overlapping diseases, which may have different aetiologies (causes), but have similar biologic, morphologic (form), and clinical outcomes. OA can arise in any synovial joint in the body, but most often in the hands, feet, spine, knees, and hip joints. Because arthritis and rheumatic diseases receive far less attention in the scientifi c literature than is warranted by their enormous and growing disease burden, this study aims to contribute to the understanding of OA, especially a frequently occurring form of OA, hand OA, and its clinical consequences for the patients. Except for one review, all other studies presented in this thesis were based on data from the Rotterdam study, a large cohort from the open population of persons aged 55 years and older in the Netherlands. Baseline measurements were conducted between 1990 and 1993 on a total of 7983 participants (response rate of 78%). Hand radiographs were made at baseline for each participant, but for feasibility reasons only 3906 radiographs were scored of which the data were used in the following studies.