Aiming to study the possible association of Dkk-1 to bone loss detected by MSK ultrasound imaging and DEXA scanning rheumatoid arthritis patients by measuring its serum levels in relation to disease activity and severity. We conducted this study on 30 RA patients and 18 apparently healthy individuals serving as a control group. All patients and controls were subjected to history taking, clinical examination, laboratory investigations, and measurement of serum levels of DKK-1. Assessment of disease activity by using modified DAS 28 score and functional disease activity by MHAQ. Disease severity was assessed by Larsen score and musculoskeletal US to detect erosive arthritis and bone mineral density was assessed by DEXA scanning. Most of RA patients had active disease with mean DAS 28-ESR was 4.96± 1.08 with 26 cases had erosive arthritis (86.7%). serum DKK-1 levels were significantly higher in patients than control group (P<0.001). Serum DKK-1 levels were higher in patients with more severe RA and positively correlated with joints erosions as assessed by Larsen score(r = 0.954, p <0.001) and ultrasound Joint erosions score (p <0.001). Serum Dkk1 in osteoporotic patients was significantly higher than in control group (P˂ 0.001). At serum DKK1 titre (1960pg/dl) it was a reliable diagnostic test of erosions in RA with sensitivity 100%.Conclusion Serum DKK-1 may be a reliable biomarker of erosive arthritis detected by US, bone erosions and osteoporosis in RA. Moreover, it was highly associated with disease activity and severity.