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trochoid joint n.
A joint in which a section of a cylinder of one bone fits into a corresponding cavity on the other, as in the proximal articulation between the radius and ulna. Also called pivot joint, rotary joint.
in vertebrate anatomy, a joint that allows only rotary movement. It is exemplified by the joint between the atlas and the axis (first and second cervical vertebrae), directly under the skull, which allows for turning of the head from side to side. Pivot joints also provide for the twisting movement of the bones of the forearm (radius and ulna) against the upper arm, a movement used, for instance, in unscrewing the lid of a jar