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Synarthroses are bound together by either fibrous (symphyses and syndesmoses) or cartilaginous tissue (synchondroses). Symphyses are joints joined by fibrocartilage, in which the two opposing surfaces are covered by hyaline cartilage (thus, symphyses are also considered cartilaginous joints). The strength of the fibrocartilage allows for only a little movement but much stability, while the hyaline cartilage on the articulating surfaces allows for shock absorption. The pubic symphyses and intervertebral joints are examples of symphyses (Figure 3.15). The adjoining bones of fibrous syndesmoses are bound together by a thin sheet of fibrous tissue, either a ligament or a fibrous membrane. Since the fibrous tissue is flexible, these joints allow partial movement. The amount of movement allowed depends on the length of the fibers uniting the bones. Examples of syndesmoses are the suture joints of the skull and the union of the radius and ulna in the forearm by an interosseous membrane. Synchrondroses are joints joined together by cartilage and permit slight bending in early life. A key example is the joining of the epiphysis of a long bone with the metaphysis by a cartilaginous growth plate (the physis) (Figure 3.14). This is a temporary synchondrosis since the growth plate eventually ossifies in the mature adult.

Table 3.7 Classifications of Joints