This trial is designed to assess if there is evidence of subclinical joint bleeding on MRI/X-Ray in adults with severe Haemophilia A while on standard and/or pharmacokinetically tailored prophylaxis regimens. Participants with severe Haemophilia A will have longitudinal MRI and XRay imaging of their elbows, ankles and knees at 0, 6 and 18 months while on standard ( 0-6 months) and then pharmacokinetically tailored (7-18 months) recombinant Factor VIII prophylaxis.