<prompt> X Ray shows lytic lesion in calceneus in young adult. Biopsy shows following diagnosisPigmented viilonodular synovitisOchronosisOsteomylitisEumycosis  <response>: Ans. a Pigmented viilonodular synovitisImage shows hyperplasia of synomin along with hemosiderin laden macrophages and giant cells so Pigmented viilonodular synovitis. 