Synovitis, a common feature in haemophilia, is triggered by the presence of blood in joints, and represents the first step towards the development of chronic arthropathy. Synovitis may be detected early by means of ultrasound or magnetic resonance imaging scan; clinical joint scores are less sensitive in this setting. Regular long-term prophylaxis with clotting factor concentrates, as primary prophylaxis and tailored to individual needs, has high efficacy in preventing synovitis. In general, higher factor levels lower bleeding risk, but no direct correlation between factor levels and synovitis incidence has been demonstrated. This study aimed to develop an expert consensus relating to the definition, pathophysiology, diagnosis, prevention, follow-up and treatment of synovitis, recognising its relevance for joint health and taking into account existing knowledge gaps. A Delphi consensus study was designed and performed. An expert group prepared 22 statements based on existing literature; a wider expert panel subsequently voted on these. Retention of panellists was high. Four statements required amending and consensus on all statements was achieved after three rounds of voting. This e-Delphi consensus study addressed the importance of synovitis in joint health of people with haemophilia and highlighted knowledge gaps in this field. Studies on the natural course of synovitis are lacking and the biological mechanisms underlying this process are not yet fully elucidated. While basic and clinical research proceeds in this field, expert consensus can help guide clinicians in their routine clinical practice, and Delphi methodology is often used to produce best-practice guidelines.