Background: The relationship between industry and the orthopaedic community is under increasing scrutiny. Industry traditionally has funded a substantial amount of the orthopaedic research published in this and other journals. The objective of the present study was to investigate associations between the level of evidence and declared source(s) of funding in papers published in the American volume of The Journal of Bone and Joint Surgery. Methods: All articles published in the American volume of The Journal of Bone and Joint Surgery from January 2003 to December 2007 were reviewed by a single individual. Primary research papers with an assigned level of evidence were assessed with regard to source of funding, subject area, and results. The association between source of funding and level of evidence was described with use of contingency tables and chi-square tests. Results: Of 886 studies with an assigned level of evidence, 246 were funded by industry, of which 124 (50%) were graded as Level-IV evidence. Among 274 studies funded by governments, foundations, or universities, only seventy-nine (29%) were graded as Level-IV evidence. Among 366 studies with no funding declared, 209 (57%) were graded as Level-IV evidence. The association between industry funding and a lower level of evidence was significant (p < 0.0001). Conclusions: While industry funded a larger number of studies than any other single source in this journal, the level of evidence of industry-funded studies was lower that that for studies funded by governments, foundations, or universities. Improving the scientific quality of industry-funded research might increase the quality of evidence for making orthopaedic decisions.