joint

joint, articulation, suture denote a place where two things are united or the mechanism by which they are united.

Joint is the most inclusive of these terms and is freely usable in reference both to anatomical and mechanical structures. In anatomical reference it applies to a junction whether rigidly fixed or capable of more or less complex movements of two skeletal parts (as vertebrate bones or cartilages or molluscan shell valves) and is the one of these terms that is equally applicable to the bodily region or part at which there is such a junction

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the knee joint

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the joint at the elbow is flexible

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he aches in every joint

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Similarly, in mechanical reference, joint applies to a junction between two parts that serves as a coupling and may be rigid

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a dovetail joint at the corner of a drawer

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a joint in a gas pipe

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mortar joints between bricks carefully finished to shed water

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or may form a flexible union

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a swivel joint

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the ball joints . . . have a lateral as well as up-and-down action, thus cushioning against bumps— Ford Times

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or even (as in a universal joint) one through which motion is transmitted from one part to the other.

Articulation is chiefly an anatomical term, though it has some extended use (see under INTEGRATE). Anatomically articulation is applicable to the same parts of the skeleton as joint but distinctively it implies, as joint does not, the fitting together or adjustment of two parts or bones with relation not only to each other but to the entire structure and its function and is therefore not applicable, as joint is, to the bodily region or part where a joint occurs. It is especially appropriate when the mechanism of a joint or the elements entering into its formation are under consideration

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ball-and-socket structure of a movable articulation

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various articulations are supported by ligaments

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the synovial membrane reduces friction at an articulation

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The word may also denote the process of joining or the adjustment in joining

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in the flat bones the articulations usually take place at the edges— Henry Gray

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Suture is used of a joint or articulation that suggests a seam or that has been brought about by sewing

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the joints of the two parts of a pea pod are called respectively the ventral and dorsal sutures

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the form of articulation observable in the skull where two flat bones meet in a line is called a suture

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Suture is used in surgery of a seam, especially of one whereby two edges of an incision are brought together so that they may ultimately unite.