However, related subchondral bone cysts with a synovial-like lining were subsequently described by Fisk in 7949 and Hicks h 7955. Over the years, various synonyms for these lesions have appeared in the literature: synovial cysts, juxta-articular bone cysts, intra-osseous ganglia, ganglion cysts of bone, and geodes. According to the \X/orld Health Organization classification of bone tumors and tumor-like lesions, the term juxta-afiicular bone cyst (intraosseous ganglion) is defined as "a benign cystic and often multi-loculated lesion made up of fibrous tissue, with extensive mucoid changes, located in the subchondral bone adjacent to a joint. Radiologically, it appears as a well-defined osteolyic lesion with a surrounding area of sclerosis. It has been described as a synovial cyst, but it lacks a synovial lining." As such, the definition excludes the cystic juxta-articular bone lesions seen in conjunction with pigmented villonodular synovitis, as well as other osteolyic bone lesions. In spite of the great number of descriptive names, these lesions share virtually the same macroscopic and microscopic characteristics. The cysts are usually solitary, but may be multilocular. They commonly develop in the epiphyseal or metaphyseal areas of bone adjacent to joints. Generally, they have a whitish or bluish lining consisting of parallel bundles of collagen. The fibrocyes lying along the inner wall of the cavity sometimes form an incomplete lining of flattened, synovial-like cells. This makes for a smooth wall within which the cyst contains a thick gelatinous mucoid fluid. Still, there are those who distinguish the subchondral bone cysts seen in conjunction with osteoarthritis or other joint damage, from intraosseous ganglia or synovial cysts of bone. The former are more likely to communicate with the joint through the articular surface in up to 400/o of the cases, and therefore may be filled with synovial fluid; whereas the latter communicate with the joint in less than 3o/o of the documented cases and the fluid is more commonly a viscous mucoid material. In fact, the Armed Forces Institute of Pathology, as late as 1977, separated as distinct entities the subchondral bone cysts and the synovial cyst of bone. Other similar cystic lesions are found in conjunction with silastic joint implants (Fig. 2), and as a consequence of the degenerative changes caused by osteochondral fractures such as those seen in the ankle joint.