19 osteoarthritic femoral heads obtained during total hip replacement procedure were studies. Photography, x-ray with mamograph and optical microscopy were then carried out. The authors analysed osteoarthritic cysts at different stages of development. By successive cuts they were able to demonstrate the communication of the cyst itself with the joint cavity. The authors believe that the filtration of synovial fluid in the subchondral bone might stimulate the proliferation of conjuntival cells
