An article published in September 2008 (A Martínez, J Varadé, J R Lamas, et al. GDF5 Polymorphism associated with osteoarthritis: risk for rheumatoid arthritis. Ann Rheum Dis 2008;67:1352–3) did not sufficiently reference the ideas published in the following article: Reines BP. Is rheumatoid arthritis premature osteoarthritis with fetal-like healing? Autoimmun Rev 2004;3:305-11. Reines's model provided a great deal of the impetus for searching for a GDF5 polymorphism associated with rheumatoid arthritis. The authors apologise for this.