Synovial membrane is traditionally considered as a part of the joint capsule. It, however, differs from fibrous part of the capsule in development, structure, function, vascularisation, innervation and involvement in pathological processes. Moreover, in some areas, it even does not contact with the fibrous capsule. Thus, it appears that the synovial membrane should be considered as an independent organ and not as the lining of the joint capsule.