Haemophilia is a bleeding disorder in which the proteins required
for blood to clot are partly or completely missing. As a result,
people with haemophilia bleed for longer than average. They bruise
easily after minor knocks and bumps, and internal bleeding can also
occur into joints, muscles and soft tissues. People with severe
haemophilia may experience spontaneous bleeding. Untreated, these
bleeds can be very serious, causing acute pain and potentially
disabling joint damage.