Objective To investigate the correlation of the receptor activator of nuclear factor kappa-B ligand (RANKL)/serum osteoprotegerin （OPG）system, Dickkopf-1 (DKK-1) and bone marrow edema(BME) in rheumatoid arthritis (RA) with the complaint of knee pain. Methods The clinical data of 50 cases of RA with the complaint of knee pain were collected. According to MRI finding, half of them (25 cases) had bone marrow edema（BME）. Each patient received the measurement of serum OPG, RANKL, DKK-1, C-reactive protein （CRP）, erythrocyte sedimentation rate （ESR）, anti cyclic citrullinated peptide antibody （CCP）, rheumatoid factor （RF）. The clinical symptoms, disease activity score 28 （DAS28）, were compared between BME and non-BME groups, and the correlation between RANKL/OPG system, DKK-1 and BME of RA was analyzed. Results Compared with non BME group, BME group had shorter course （\P=0.000）, higher DAS28 score (\P=0.009), CRP (\P=0.000), RF (\P=0.033) and CCP (\P=0.012) . lower level of serum OPG (\P=0.000), higher level of RANKL (\P=0.000), RANKL/OPG (\P=0.000), and DKK-1 (\P=0.001).The severity of bone marrow edema was correlated with the serum RANKL (volume \rs=0.31, \P=0.027; degree \rs=0.33, \P=0.022), RANKL / OPG (volume \rs=0.29, \P=0.039; degree \rs=0.28, \P=0.043), DKK-1 (volume \rs=0.33, \P=0.021; degree \rs=0.34, \P=0.019). Conclusion BME is one of the early signs of bone erosion in RA, there were more active inflammation, autoantibodies, and osteocasts in RA patients with BME.
