The Osteoarthritis Initiative (OAI) is a multicenter, longitudinal, prospective observational study of knee osteoarthritis (OA), currently in its 14th year of follow up. This Initiative is a public-private partnership between the NIH and private industry that seeks to develop a public-domain research resource to facilitate the scientific evaluation of biomarkers for osteoarthritis as potential surrogate endpoints for disease onset and progression. Technical details on study start-up, protocol development, and recruitment and enrollment are available on the OAI website.

OAI Biospecimens

Biospecimens have been collected from OAI study participants, including serum, plasma, urine, and DNA. We encourage interested investigators to apply for use of these limited resources. Learn more about how to apply for OAI biospecimens.


The OAI cohort of 4,796 participants is 58% female and ranged in age from 45-79 at time of recruitment. Retention remained high throughout the study duration. Some participants (about 7%) from the original cohort did not continue for the additional five years of follow up. The rate of no-contact stabilized in the 15-18% range. The entire OAI cohort has completed:

  • Baseline, 12-month, 24-month, 36-month, and 48-month visits in clinic with biospecimen collection and imaging
  • 60-month and 84-month visits via mailed questionnaires and telephone interviews
  • 72-month visit in clinic with biospecimen collection and imaging
  • 96-month visit in clinic with imaging

The above visits were completed as of January 1, 2015. The follow up continues for subsets of the cohort. There are biological specimens available for baseline, 12-month, 24-month, 36-month, 48-month and the 72-month visits. A subset of participants in the progression cohort were also seen at 18 months (n=288) or 30 months (n=494) for knee MRI, blood collection, exam and questionnaire data to allow for analysis of change over shorter intervals.

Research Teams

The OAI research team consisted of the following centers and their principal investigators: University of Maryland School of Medicine, Baltimore: Marc Hochberg, M.D., M.P.H.; The Ohio State University, Columbus: Rebecca Jackson, M.D.; University of Pittsburgh: C. Kent Kwoh, M.D.; Memorial Hospital of Rhode Island, Pawtucket: Charles Eaton, M.D.; and University of California, San Francisco: Michael Nevitt, Ph.D. A Steering Committee, comprised of representatives from these centers, the NIH, and the pharmaceutical partners, advised on the scientific aspects of the study. A representative from the U.S. Food and Drug Administration also advised the Steering Committee.

Data and Images Released

Data and images have been publicly released through the OAI Online website since 2004. Data and images from all visits are currently available on the OAI website. Additional data from image and biospecimen analyses are posted quarterly on the OAI website. As of March 23, 2016, there were 4,114 registered users of OAI Online from more than 90 countries, with over 30,260 datasets downloaded and 507 image sets distributed. To date, clinical data, images, and biospecimens are available for visits through 96 months. Over 300 manuscripts have been produced and published to date based on use of the OAI data and images.

In 2010, the NIAMS funded three contracts for analysis of OAI data to Dr. Charles Eaton at Memorial Hospital of Rhode Island, for "Osteoarthritis Patient-centered Outcomes and Complementary and Alternative Therapy (CAM)"; to Dr. C. Kent Kwoh at University of Pittsburgh, for "Pivotal Osteoarthritis Initiative Magnetic Resonance Imaging Analyses"; and to Dr. Michael Nevitt at University of California, San Francisco, for "Hip Morphology and Limb-specific Risk Factors for Radiographic Hip Osteoarthritis." All of these contracts have been completed. Publications from completed analyses are being published yearly. New data generated from these studies are currently being posted on the OAI Online website.


Both NIH and private sector participants have contributed funding for the OAI. The private sector funding was initially provided by Pfizer, Merck, GlaxoSmithKline, and Novartis. The Foundation for the National Institutes of Health (FNIH) has coordinated private sector participation. Funding from the NIH institutes and centers initially included NIAMS, the National Institute on Aging (NIA), the National Center for Complementary and Integrative Health (NCCIH, formerly known as the National Center for Complementary and Alternative Medicine), the National Institute on Minority Health and Health Disparities (NIMHD), the National Institute of Dental and Craniofacial Research (NIDCR), the NIH Office of Research on Women’s Health (ORWH), and the National Institute for Biomedical Imaging and Bioengineering (NIBIB). Financial support for the extension of follow up for the OAI cohort (additional four contacts, 2010-2014) has been provided by Pfizer and Novartis from the private sector and the NIAMS, NIA, NCCIH, NIMHD, ORWH, and NIBIB.

This groundbreaking study is expected to advance our understanding of how modifiable and non-modifiable risk factors are linked to development and worsening of knee osteoarthritis. Such findings may, in turn, lead to improved strategies for prevention of disease and identification of novel treatment targets, which could result in prevention of later-life disability in individuals with knee osteoarthritis.

Learn more about the history of the OAI.

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