Despite the use of primary prophylactic Factor VIII replacement in severe hemophilia A patients, bleeding into joints cannot be prevented completely and early diagnosis and treatment of the joint bleedings are important for prevention of permanent joint damage. Recent studies have shown that neoangiogenesis plays important role in development of synovitis after recurrent joint bleedings. This study aimed to investigate the relationship between joint findings and levels of serum angiogenic and inflammatory factors in severe hemophilia A patients.The patient groups consisted of 10 severe hemophilia A patients with acute joint bleeding and 25 severe hemophilia A patients without acute joint bleeding. They were all inhibitor negative. The control group consisted of 22 healthy male children. Complete blood cell count analysis, C-reactive protein (CRP), serum ferritin, lactic acid, and ELISA-based detection of vascular endothelial growth factor (VEGF), intercellular adhesion molecule-1, thrombomodulin, macrophage migration inhibitory factor (MIF), and endostatin were performed from peripheral blood of patient and the control groups. CRP and MIF levels were detected significantly higher in hemophilia patients with acute joint bleeding than patients without acute joint bleeding. There was a positive correlation between serum thrombomodulin, VEGF, and MIF levels. In this study, we demonstrated that serum CRP and MIF levels increases in acute bleeding period regardless of the presence of previous joint damage in children with severe hemophilia. CRP elevation may be a useful and rapid marker for acute bleeding in these patients.