IL-6 with the soluble IL-6 receptor triggered osteoclast formation and has also been associated with osteoclast-like cell formation in rheumatoid arthritis patients and may contribute to bone resorption [72,73], which supports our observation of an association between increased synovial fluid IL-6 concentrations and decreasing bone fraction in the medial tibial plateau. Here, IL6 is linked to rheumatoid arthritis.