For the purposes of classification, it should be specified whether osteoarthritis (OA) of the knee is of unknown origin (idiopathic, primary) or is related to a known medical condition or event (secondary). Clinical criteria for the classification of idiopathic OA of the knee were developed through a multicenter study group. ____and radiographs were used to develop sets of criteria that serve different investigative purposes. In contrast to prior criteria, these proposed criteria utilize classification trees, or algorithms.

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THE TECUMSEH COMMUNITY HEALTH STUDY (TCHS) was not undertaken solely as a rheumatic disease survey but as a broad study of health and disease in a total community setting. [l, 21 It was conceived as a continuing dynamic study of the multitude of natural processes and interactions which are responsible for the maintenance of health or the development of disease. Interest has centered not so much on the identification of established disease as on the possibility of elucidating the early origins of disease and identifying those apparently healthy individuals with a predisposition to disease. The focus has been on the family unit and kindred since the working hypothesis has been that if genetic or environmental factors are operative in the production of a given disease then actual or potential viotims should cluster about the identifiable index cases. After careful study the community of Tecumseh, Michigan was selected as the site of (the study in 1957. Tecumseh is located in southeastern Michigan approximately 30 miles from AM Arbor. Its size of 9500 was considered adequate and yet small enough to make an ambitious study practicable. It is located in a rural agricultural area but also has a large manufacturing plant so that a variety of socioeconomic groups are present. Available information indicated the relative stability of the population and a friendly cooperative community spirit was apparent. In 1957 a complete census of the town was undertaken and all inhabitants charted by households and kindreds. Self-reported information was obtained regarding forty chronic health conditions including "arthritis", "rheumatism" and chronic back pain. During 1957 and 1958 several pilot studies, including an investigation of cerebral palsy, a prophylactic trial of influenza vaccine and a study of the relationship between blood group,s and fertility, were successfully concluded. METHOlDS OF STUDY The present phase of the study wlas designed to obtain medical historical information, a physical examination and certain physical and laboratory measurements

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Radiographs of the fingers and wrists of adult participants in the Tecumseh Community Health Study in 1962-65 were examined for signs of osteoarthritis (OA). The severity of OA for each of 32 joints of the fingers and wrists was recorded for each individual. Attention was restricted to the 3035 participants who were 32 years of age or older and for whom a diagnosis of OA was available for each of 32 joints. Joint-specific prevalence rates of OA increased sharply with age for both sexes, and at the older ages, the prevalence rates for most joints were higher for females. Older individuals with OA also had a greater number of affected joints, with females having a greater number of affected joints than males. Of those individuals aged 44 years or younger, only 6.2% had one or more joints affected with OA. The percentages were 21.6 and 42.0% for those aged 45-59 years and 60 or more years, respectively. The distal interphalangeal (DIP) joints were the most frequently affected joints in all age categories for both sexes and OA in the proximal interphalangeal (PIP) joints was positively associated with OA in the DIP joints. However, controlling for the number of affected DIP joints, the PIP joints of older subjects were more likely to exhibit OA than the PIP joints of younger subjects. Though there is an association between OA in the DIP and PIP joints, there was only a small, nonsignificant association (OR = 1.24, 95% CI = 0.83, 1.84) between disease in the DIP and PIP joints of the same finger.