The most common cause of these dislocations is a fall on the outstretched hand, the forearm at the moment being strongly pronated. Forced abduction favours the displacement to the ulnar side; adduction to the radial side. The limb is held flexed and pronated, and the facility with which the bony points can be palpated renders the diagnosis easy. In a few cases _diverging dislocations_ have been met with, the radius and ulna being separated from one another, the annular (orbicular) ligament being torn and no longer holding them together. #Treatment of Dislocations of Elbow.#--The chief obstacle to reduction is the spasmodic contraction of the muscles passing over the joint, and, in the backward variety, the hitching of the coronoid process against the edge of the olecranon fossa. In recent cases, to effect reduction the patient is seated on a chair, while the surgeon grasps the humerus and wrist, and places his knee in the bend of the elbow. The limb is first fully extended, or even hyper-extended, to relax the triceps and free the coronoid process. Traction is then made in opposite directions upon the forearm and arm, the surgeon's knee meanwhile making pressure, in a backward direction, upon the lower end of the humerus. The joint is next slowly flexed, and the bones slip into position, often with a distinct snap. If the patient be anæsthetised, these manipulations must be adapted to the recumbent position. When some days have elapsed before reduction is attempted, forcible manipulations are to be deprecated as they greatly increase the risk of ossification occurring in relation to the brachialis (D. M. Greig); and recourse should be had to open operation, and the tearing or bruising of the soft parts should be reduced to a minimum. After reduction, the limb is flexed to rather less than a right angle and supported by a sling. Massage and movement are commenced at once. Fracture of the coronoid process predisposes to recurrence of the dislocation; when this complication exists, therefore, the limb should be fixed at an acute angle, and movements of full extension postponed for a fortnight. Massage and limited movements, however, may be carried out from the first. If there is a fracture of the olecranon, the treatment must be modified accordingly (p. 87). [Illustration: FIG. 39.--Forward Dislocation of Elbow, with Fracture of Olecranon. (Sir Robert Jones' case. Radiogram by Dr. D. Morgan.)] Comminuted and compound injuries usually call for operative treatment, the fractured bones being wired after reduction of the dislocation, or the loose fragments removed. The _forward dislocation_ is reduced by fully flexing the elbow, and then pushing the bones of the forearm backward, while the humerus is pulled forward.