Amphiarthroses

Amphiarthroses are joints that permit limited, or slightly movable, articulation between adjacent bones. They occupy an intermediate position in the spectrum of joint mobility, with more movement than a synarthrosis (immovable) but less than a diarthrosis (freely movable). Structural support is provided by ligaments or fibrocartilaginous connections that resist large movements while allowing some flexibility.

There are two main structural varieties of amphiarthrosis. Fibrous amphiarthroses, or syndesmoses, join bones by interosseous ligaments and membranes, as in the distal tibiofibular joint. These joints provide stability with a small amount of give. Cartilaginous amphiarthroses, or symphyses, connect bones by fibrocartilage or a fibrocartilaginous disc, offering cushioning and restrained motion; well-known examples include the pubic symphysis and the intervertebral joints where fibrocartilage discs unite adjacent vertebrae.

Functionally, amphiarthroses support weight transmission and bending stresses while accommodating movement and shock, without the full range of motion seen in diarthroses. They can be affected by degeneration or injury affecting the connective tissue, such as disc degeneration in the spine or ligamentous sprains at syndesmoses.