**3. Conclusion**

In this chapter, we give an overview of the role of fibrin in the pathogenesis of synovitis. In doing so, we have neither solved the paradigm about what starts first nor discovered what triggers the invasive behaviour of rheumatoid synovial fibroblasts. Instead we provide some lines of thinking supporting the "inside – out pathway" as it has recently been named (Schett & Firestein, 2010).

The "fibrin pathway" has been little explored in rheumatoid arthritis therapeutics. The balance between clotting and dissolution of fibrin is a candidate process to target that could help to retard joint destruction.
