Trochlea of humerus

The medial portion of the articular surface of distal humerus is named the trochlea, and presents a deep depression between two well-marked borders; it is convex from before backward, concave from side to side, and occupies the anterior, lower, and posterior parts of the extremity.

The lateral border separates it from the groove which articulates with the margin of the head of the radius.

The medial border is thicker, of greater length, and consequently more prominent, than the lateral.

The grooved portion of the articular surface fits accurately within the semilunar notch of the ulna; it is broader and deeper on the posterior than on the anterior aspect of the bone, and is inclined obliquely downward and forward toward the medial side.