The most commonly involved locations include ends (epiphyses) of long bones - distal femur, proximal tibia and distal radius. Roughly half of all cases occur around the knee joint. Sarcum is another common location. Plain radiographs will show an expanding lytic lesion in an epiphyseal location extending to the articular cartilage. Usually there is no surrounding sclerosis or periosteal reaction. Destruction of the cortex and extension into soft tissue may be seen.