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Epidemiology Study




3026 (Existing Cohort); 1500 (New Cohort)






Little is known about the development of osteoarthritis or its progression and, currently, there are few strategies to prevent this condition and minimize disablement in those with existing knee osteoarthritis. The Multicenter Osteoarthritis Study (MOST) is the first large-scale epidemiologic study to focus on symptomatic osteoarthritis of the knee in a community-based sample of adults with or at high risk for knee osteoarthritis, based on the presence of knee symptoms, history of knee injury or surgery or being overweight.

The main purpose of the study is to investigate the etiology of osteoarthritis and opportunities for prevention and treatment of knee osteoarthritis by evaluating potentially modifiable risk factors for disease and poor pain and physical function outcomes, including among those with early or mild knee symptoms. MOST aims to identify modifiable biomechanical factors (including physical activity-related and gait factors), bone and joint structural factors (including those assessed by MRI of the knee), and nutritional and biochemical factors that affect the occurrence and progression of osteoarthritis-related knee symptoms and radiographic knee osteoarthritis. The ultimate goal is to contribute to the identification of novel strategies to prevent disease at an early stage and to limit the impact of disease once it has occurred.


Osteoarthritis is the most prevalent form of arthritis and the major cause of activity limitation and physical disability in older adults. Over half of those ≥ 65 years of age show radiological evidence of osteoarthritis in at least one joint. By 2030, it is expected that 20% of Americans (about 70 million people) will be at increased risk for the disease. Currently, about 39 million Americans (13% of the population) are 65 years and older, and more than half have already developed osteoarthritis. The knee is the weight-bearing joint most commonly affected by osteoarthritis. For obese individuals, the risk to develop osteoarthritis increases to two in three, accounting for many of the millions suffering from knee osteoarthritis in the United States and contributing annually to billions of dollars in excess health care costs.

Study Design

MOST is a longitudinal, prospective, observational study of knee osteoarthritis in older Americans with the disease or at increased risk of developing it. The study is comprised of two clinical centers, a data coordinating center, and an analysis center. Beginning in 2003, 3026 individuals aged 50-79 years were enrolled. Approximately 15% of this “Original Cohort” are African Americans and 60% are women. Examinations at baseline, and 15, 30, 60, 72 (telephone interview) and 84 months included assessment of risk factors, OA disease characteristics, physical function and disability, and measures of physical activity, strength, gait and quantitative sensory testing. At each clinical assessment, radiological assessments of OA (x-rays and MRI) were obtained. In 2016-2018 the cohort was enriched by the recruitment of an additional 1,500 "New Cohort" participants with early or mild knee symptoms and x-ray findings of OA. The “New Cohort” and surviving participants without end-stage knee osteoarthritis in the “Original Cohort” were asked to participate in clinic visits and telephone follow-up contacts at 144- ,152- 160- and 168-months. (Public use datasets from these four timepoints will be available in 2023.)


The MOST “Original Cohort” has been followed through 84 months. Analyses and publications using the these data have addressed multiple investigative themes, including biomechanical risk factors, causes of knee symptoms, impacts of knee OA on function and disability, and the long-term disease trajectory of knee osteoarthritis. Biological specimen samples (blood and urine) were collected at baseline, 30 months, and 60 months, and have been analyzed for biochemical variables of interest. Longitudinal readings of baseline, 15-month, 30-month, 60-month, and 84-month knee x-rays have been completed. Semiquantitative readings of selected baseline, 15-month, 30-month, 60-month, and 84-month knee MRIs have also been completed.


The participant retention rate in MOST is excellent and makes the wealth of information from this study very valuable and supportive of a wide array of opportunities for etiological, prevention, outcomes, rehabilitation and other types of research.