<prompt> A ten-year old girl presents with swelling of one knee joint. All of the following conditions can be considered in the differential diagnosis except -TuberculosisJuvenile rheumatoid ahritisHaemophiliaVillonodular synovitis  <response>: Ans. is c i.e., Haemophilia Although all conditions mentioned in the options may produce swelling of one knee joint, the clue lies in the fact that haemophilia is an X Linked recessive disease and is not manifested in girls who act only as carriers. 