Although an increased production of IL-10 and TNF-α from whole blood associates with the progression in knee osteoarthritis26, and preliminary results indicate that local and circulating cytokine concentrations decrease with severe compared to moderate knee osteoarthritis27,28, it is unknown if the circulating pro- to anti-inflammatory cytokine balance (i.e., ratio) is altered with the radiographic severity in knee osteoarthritis. This evidence concerns the gene TNF and osteoarthritis, knee.