Footnotes

• Funding This work was supported by EC framework 7 programme grant 200800 TREAT-osteoarthritis, Arthritis Research UK (ARUK), the Medical Research Council (UK), the Oxford NIHR Musculoskeletal Biomedical Research Unit, the Estonian Science Foundation grant no 5308, the Estonian Ministry of Social Affairs grants no 9.6-4/2035 and 12.1-5/597 and by AstraZeneca, Macclesfield, UK. The generation and management of genome-wide association genotype data for the Rotterdam Study is supported by The Netherlands Organisation of Scientific Research NWO Investments (no 175.010.2005.011, 911-03-012). This study is funded by the Research Institute for Diseases in the Elderly (014–93-015; RIDE2) and The Netherlands Genomics Initiative (NGI)/Netherlands Organisation for Scientific Research (NWO) (project no 050-060–810).

• Competing interests RM is an Astra Zeneca plc employee and owns Astra Zeneca stock. All other authors declare no competing interests.

• Patient consent Obtained.

• Ethics approval This study was conducted with the approval of the the Nottingham case–control and the GOAL study protocols were approved by the Nottingham City Hospital and North Nottinghamshire ethical committees. The Hertfordshire Cohort Study was approved by the East and North Hertfordshire ethical committees. The medical ethics committee of Erasmus University Medical School approved the Rotterdam study III. The Ethics Committee of the University of Tartu approved the Estonian knee osteoarthritis study.

• Provenance and peer review Not commissioned; externally peer reviewed.