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Abstract The elbow joint includes two articulations: (l) The humero-ulnar, between the trochlea of the humerus and the trochlear notch of the ulna and, (2) The humero-radia, between the capitulum of the humerus and the facet on the head of the radius. It is hence a compound synovial joint. Its complexity is increased further by its continuity with the superior radio - ulnar joint and the complete articular complex is called the cubital articulation. (1) a) The articular surfaces: are the trochlea and capitulum of the humerus, on one side, and the trochlear notch of the ulna and the head of the radius, on the other. The trochlea is not a part of a simple pully, because its medial flange is much more extensive than the lateral flange and projects downwards to a lower level so that the line of the joint, which is roughly 2 cm below the line joining the two epicondyles passes downwards and medially. In addition, the trochlea is widest posteriorly and, in this position, its lateral edge is a sharp rim .The trochlear notch is by no means perfectly congruent with the trochlea. In full extension the medial part of its upper (olecranon) half is not in contact with the trochlea, and a corresponding strip on the lateral side loses contact on flexion. |