Annular ligament

Infobox Ligament
Name = Annular ligament
Latin = ligamentum annulare radii
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Caption = Capsule of elbow-joint (distended). Anterior aspect.


Caption2 = Annular ligament of radius, from above. The head of the radius has been sawn off and the bone dislodged from the ligament.
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The Annular Ligament (orbicular ligament) is a strong band of fibers, which encircles the head of the radius, and retains it in contact with the radial notch of the ulna.

It forms about four-fifths of the osseo-fibrous ring, and is attached to the anterior and posterior margins of the radial notch; a few of its lower fibers are continued around below the cavity and form at this level a complete fibrous ring.

Its upper border blends with the anterior and posterior ligaments of the elbow, while from its lower border a thin loose membrane passes to be attached to the neck of the radius; a thickened band which extends from the inferior border of the annular ligament below the radial notch to the neck of the radius is known as the quadrate ligament.

The superficial surface of the annular ligament is strengthened by the radial collateral ligament of the elbow, and affords origin to part of the supinator. Its deep surface is smooth, and lined by synovial membrane, which is continuous with that of the elbow-joint.

The annular ligament provides stability to the radius against distal dislocation. Children who have not finished fusing their proximal radial epiphyseal plate may suffer dislocations of this joint. This frequently happens when parents sharply jerk their children by their arms, i.e. the act of grabbing a child away from traffic.

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