synovial joints are uniquely characterised by the presence of a fluid-filled synovial cavity situated between the articulating surfaces of two bones . This specific anatomical arrangement allows for considerable movement, playing a vital role in locomotion . The pivot joint between the atlas and axis is explicitly cited as an example of a synovial joint . Other options are incorrect because skull bones are connected by fibrous joints that permit no movement , and the fluid within these joints is synovial fluid, not lymph .